# Crucible `assets` Builder Implementation Plan

> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.

**Goal:** Add a self-contained `crucible assets` builder with seven commands (compile, convert, upscale, check-mdl, fix-mdl, check-dupes, clean-dupes) that fold the NWN:EE asset tools into Crucible.

**Architecture:** A new `internal/assets` package exposes `Run(args, stdout, stderr, getenv) int`, mirroring `internal/depot` exactly. `internal/dispatch` gets one `Registry` entry and one added direct-delegate branch so `crucible assets …` routes to `assets.Run` instead of the legacy `app.Run`. A pure-Go `internal/assets/mdl` package ports the model-name logic from `mdl-name-lib.sh` / `mdl-scan.awk`. External tools (the NWN engine, ImageMagick, an upscaler) are discovered on `PATH` / standard install roots and invoked through one swappable `runner` indirection so tests never call them for real.

**Tech Stack:** Go (standard library only — `os/exec`, `flag`, `image/png` in tests). ImageMagick `magick` for `convert`. The NWN:EE engine for `compile`. ncnn-vulkan upscalers for `upscale`.

## Global Constraints

- Go module path: `git.westgate.pw/ShadowsOverWestgate/sow-tools`. All internal imports use this prefix.
- **No configuration files. Arguments only.** No staging dirs, YAML, or reports. Operate in place on the target directory.
- **Fail closed, never fake** (Crucible rule #1). A missing backend is a clear error naming what to install and a non-zero exit — never a placeholder artifact.
- Exit codes (assets-local, sysexits-style): `0` OK, `1` problems found / per-file failures, `64` usage (unknown subcommand, bad flags), `70` missing external tool / internal error.
- `assets.Run` signature is exactly `func Run(args []string, stdout, stderr io.Writer, getenv func(string) string) int` — identical to `depot.Run`. No direct use of `os.Stdout`/`os.Getenv` inside command logic; everything flows through the passed writers and `getenv`.
- External-command calls go through the package-level `runner` variable (defined in Task 2) so tests swap it. Never call `exec.Command` directly outside `runner`.
- `make check` (go vet + go test + shellcheck + yamllint) must stay green. `make smoke` must include `assets` in its wired list.
- Follow the existing code style: package doc comments, lowercase-first error strings, table-driven tests, `t.TempDir()` for fixtures.

---

## File Structure

**New files:**
- `internal/assets/mdl/mdl.go` — pure-Go model-name module (`IsASCII`, `ExpectedName`, `CheckNames`, `FixNames`).
- `internal/assets/mdl/mdl_test.go` — table-driven parity fixtures.
- `internal/assets/run.go` — `Run` dispatch, usage, exit constants.
- `internal/assets/helpers.go` — `walk`, `look`, `runner`.
- `internal/assets/dupes.go` — `check-dupes` + `clean-dupes`.
- `internal/assets/checkmdl.go` — `check-mdl`.
- `internal/assets/fixmdl.go` — `fix-mdl`.
- `internal/assets/convert.go` — `convert` + shared `ddsToPNG`/`pngToDDS` helpers.
- `internal/assets/upscale.go` — `upscale`.
- `internal/assets/compile.go` — `compile`.
- `internal/assets/*_test.go` — one test file per command file above.
- `cmd/crucible-assets/main.go` — one-line shim.

**Modified files:**
- `internal/dispatch/dispatch.go` — Registry entry + delegate branch.
- `internal/dispatch/dispatch_test.go` — extend canonical-surface and metadata tests.
- `scripts/crucible-smoke.sh` — add `assets` to wired list.
- `docs/command-surface.md` — seven visible-command rows.

---

## Task 1: `internal/assets/mdl` model-name module

**Files:**
- Create: `internal/assets/mdl/mdl.go`
- Test: `internal/assets/mdl/mdl_test.go`

**Interfaces:**
- Produces:
  - `type Mismatch struct { Line int; What string; Got string }` — `Line` is 1-based, `0` for the geometry base-node mismatch (which has no line).
  - `func IsASCII(path string) (bool, error)`
  - `func ExpectedName(path string) string`
  - `func CheckNames(path string) ([]Mismatch, error)`
  - `func FixNames(in []byte, expected string) (out []byte, changed bool)`

Detection must match `mdl-scan.awk` (`../sow-assets-manifest/scripts/mdl-scan.awk`) because that awk keeps running in `sow-assets-manifest` until a follow-up spec retires it. Comparisons are case-insensitive against the file stem.

- [ ] **Step 1: Write the failing test**

Create `internal/assets/mdl/mdl_test.go`:

```go
package mdl

import (
	"os"
	"path/filepath"
	"testing"
)

func writeMDL(t *testing.T, name, body string) string {
	t.Helper()
	p := filepath.Join(t.TempDir(), name)
	if err := os.WriteFile(p, []byte(body), 0o644); err != nil {
		t.Fatal(err)
	}
	return p
}

func TestIsASCII(t *testing.T) {
	ascii := writeMDL(t, "foo.mdl", "newmodel foo\nbeginmodelgeom foo\n")
	if ok, err := IsASCII(ascii); err != nil || !ok {
		t.Fatalf("ascii: ok=%v err=%v, want true nil", ok, err)
	}
	bin := writeMDL(t, "bar.mdl", "\x00\x01binary\x00garbage")
	if ok, err := IsASCII(bin); err != nil || ok {
		t.Fatalf("binary: ok=%v err=%v, want false nil", ok, err)
	}
	hash := writeMDL(t, "baz.mdl", "# a comment\nnewmodel baz\n")
	if ok, _ := IsASCII(hash); !ok {
		t.Fatal("leading # should be ascii")
	}
}

func TestExpectedName(t *testing.T) {
	for in, want := range map[string]string{
		"a/b/Foo.MDL": "Foo",
		"waxbt_b_091.mdl": "waxbt_b_091",
		"x.mdl": "x",
	} {
		if got := ExpectedName(in); got != want {
			t.Errorf("ExpectedName(%q)=%q want %q", in, got, want)
		}
	}
}

func TestCheckNames(t *testing.T) {
	// Header token mismatch + base-node mismatch in one file.
	body := "newmodel wrong\n" +
		"setsupermodel wrong a_base\n" +
		"beginmodelgeom foo\n" +
		"  node dummy Wmgst_m_081\n" +
		"    parent null\n" +
		"  endnode\n" +
		"endmodelgeom foo\n" +
		"donemodel foo\n"
	p := writeMDL(t, "foo.mdl", body)
	got, err := CheckNames(p)
	if err != nil {
		t.Fatal(err)
	}
	// Expected stem "foo": newmodel(wrong), setsupermodel(wrong), base node(Wmgst_m_081).
	if len(got) != 3 {
		t.Fatalf("got %d mismatches, want 3: %+v", len(got), got)
	}
	if got[0].What != "newmodel" || got[0].Got != "wrong" || got[0].Line != 1 {
		t.Errorf("first mismatch = %+v", got[0])
	}
	base := got[len(got)-1]
	if base.What != "root node" || base.Got != "Wmgst_m_081" || base.Line != 0 {
		t.Errorf("base mismatch = %+v", base)
	}

	// Clean model -> no mismatches.
	clean := writeMDL(t, "bar.mdl",
		"newmodel bar\nbeginmodelgeom bar\n  node dummy bar\n    parent null\n  endnode\nendmodelgeom bar\ndonemodel bar\n")
	if got, _ := CheckNames(clean); len(got) != 0 {
		t.Fatalf("clean model reported mismatches: %+v", got)
	}

	// Binary model -> nil, no error.
	bin := writeMDL(t, "b.mdl", "\x00\x00binary")
	if got, _ := CheckNames(bin); got != nil {
		t.Fatalf("binary reported mismatches: %+v", got)
	}
}

func TestFixNamesRoundTrips(t *testing.T) {
	body := "newmodel wrong\n" +
		"setsupermodel wrong\n" +
		"beginmodelgeom wrong\n" +
		"  node dummy Wmgst_m_081\n" +
		"    parent null\n" +
		"  endnode\n" +
		"endmodelgeom wrong\n" +
		"donemodel wrong\n"
	out, changed := FixNames([]byte(body), "foo")
	if !changed {
		t.Fatal("expected changed=true")
	}
	p := filepath.Join(t.TempDir(), "foo.mdl")
	if err := os.WriteFile(p, out, 0o644); err != nil {
		t.Fatal(err)
	}
	got, err := CheckNames(p)
	if err != nil {
		t.Fatal(err)
	}
	if len(got) != 0 {
		t.Fatalf("fixed model still has mismatches: %+v\n%s", got, out)
	}
	// Idempotent: fixing a clean model changes nothing.
	if _, changed := FixNames(out, "foo"); changed {
		t.Fatal("second fix reported a change")
	}
}
```

- [ ] **Step 2: Run test to verify it fails**

Run: `go test ./internal/assets/mdl/`
Expected: FAIL — package/functions do not exist.

- [ ] **Step 3: Write the implementation**

Create `internal/assets/mdl/mdl.go`:

```go
// Package mdl ports the ASCII MDL model-name checks from sow-assets-manifest's
// mdl-name-lib.sh + mdl-scan.awk to pure Go. Binary (compiled) MDLs are opaque
// here; the NWN engine is the validator for those. Detection mirrors
// mdl-scan.awk exactly so behavior does not drift while that awk still runs in
// sow-assets-manifest.
package mdl

import (
	"bytes"
	"os"
	"path/filepath"
	"strings"
)

// Mismatch is one model-name problem. Line is 1-based; 0 means the geometry
// base-node mismatch, which the source has no single line for.
type Mismatch struct {
	Line int
	What string
	Got  string
}

// ExpectedName is the file stem with a trailing ".mdl" (any case) removed.
func ExpectedName(path string) string {
	base := filepath.Base(path)
	if len(base) >= 4 && strings.EqualFold(base[len(base)-4:], ".mdl") {
		return base[:len(base)-4]
	}
	return base
}

// IsASCII reports whether path is an uncompiled ASCII model: no NUL in the
// first 256 bytes, and a leading keyword of '#' / newmodel / node /
// setsupermodel. Mirrors mdl_is_ascii.
func IsASCII(path string) (bool, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return false, err
	}
	return isASCII(data), nil
}

func isASCII(data []byte) bool {
	head := data
	if len(head) > 256 {
		head = head[:256]
	}
	if bytes.IndexByte(head, 0) >= 0 {
		return false
	}
	line := head
	if i := bytes.IndexByte(line, '\n'); i >= 0 {
		line = line[:i]
	}
	trimmed := strings.TrimLeft(string(line), " \t\r")
	if strings.HasPrefix(trimmed, "#") {
		return true
	}
	fields := strings.Fields(trimmed)
	if len(fields) == 0 {
		return false
	}
	tok := strings.ToLower(fields[0])
	return strings.HasPrefix(tok, "newmodel") ||
		strings.HasPrefix(tok, "node") ||
		strings.HasPrefix(tok, "setsupermodel")
}

// lineFields splits a line into whitespace-delimited tokens with the trailing
// CR removed, matching awk's default field split + \r strip.
func lineFields(line string) []string {
	return strings.Fields(strings.TrimRight(line, "\r"))
}

// field returns the 1-based nth field or "" if absent.
func field(f []string, n int) string {
	if n >= 1 && n <= len(f) {
		return f[n-1]
	}
	return ""
}

// CheckNames returns every model-name mismatch in an ASCII model. Returns nil
// for a binary model or one with no newmodel line (not a real model).
func CheckNames(path string) ([]Mismatch, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}
	if !isASCII(data) {
		return nil, nil
	}
	return checkNames(data, ExpectedName(path)), nil
}

func checkNames(data []byte, expected string) []Mismatch {
	expLower := strings.ToLower(expected)
	var out []Mismatch
	seenModel := false
	inGeom := false
	curNode := ""
	base := ""
	baseFound := false

	// header records one header-token mismatch (field n, 1-based) if the token
	// is present and differs case-insensitively from the stem.
	lines := strings.Split(string(data), "\n")
	for i, raw := range lines {
		f := lineFields(raw)
		if len(f) == 0 {
			continue
		}
		key := strings.ToLower(f[0])
		mis := func(what string, n int) {
			got := field(f, n)
			if got != "" && !strings.EqualFold(got, expected) {
				out = append(out, Mismatch{Line: i + 1, What: what, Got: got})
			}
		}
		switch key {
		case "newmodel":
			seenModel = true
			mis("newmodel", 2)
		case "setsupermodel":
			mis("setsupermodel model", 2)
		case "beginmodelgeom":
			inGeom = true
			mis("beginmodelgeom", 2)
		case "endmodelgeom":
			inGeom = false
			mis("endmodelgeom", 2)
		case "donemodel":
			mis("donemodel", 2)
		case "newanim":
			mis("newanim model", 3)
		case "doneanim":
			mis("doneanim model", 3)
		case "node":
			if inGeom {
				curNode = field(f, 3)
			}
		case "parent":
			if inGeom && !baseFound && strings.EqualFold(field(f, 2), "null") {
				base = curNode
				baseFound = true
			}
		}
	}
	if !seenModel {
		return nil
	}
	if baseFound && base != "" && !strings.EqualFold(base, expLower) {
		out = append(out, Mismatch{Line: 0, What: "root node", Got: base})
	}
	return out
}

// FixNames rewrites only the model identity to expected: the header tokens plus
// the geometry base node's declaration / any parent / animroot pointing at the
// old base name. Animation bone names and supermodel animroots are left alone
// so inheritance keeps working. Mirrors mdl_fix_model_name in intent.
//
// ponytail: a rewritten line is rebuilt joining fields with single spaces and
// drops a trailing CR, exactly like the awk it replaces; unchanged lines are
// byte-identical. The engine ignores identity-line whitespace, and FixNames'
// contract is only "produces a model that passes CheckNames", not byte parity.
func FixNames(in []byte, expected string) (out []byte, changed bool) {
	if !isASCII(in) {
		return in, false
	}
	// oldbase: the base-node name to rename, only if it differs from expected.
	oldbase := ""
	for _, m := range checkNames(in, expected) {
		if m.What == "root node" {
			oldbase = m.Got
		}
	}

	lines := strings.Split(string(in), "\n")
	for idx, raw := range lines {
		f := lineFields(raw)
		if len(f) == 0 {
			continue
		}
		key := strings.ToLower(f[0])
		set := func(n int) bool {
			if field(f, n) == "" {
				return false
			}
			f[n-1] = expected
			return true
		}
		modified := false
		switch key {
		case "newmodel", "setsupermodel", "beginmodelgeom", "endmodelgeom", "donemodel":
			modified = set(2)
		case "newanim", "doneanim":
			modified = set(3)
		case "node":
			if oldbase != "" && strings.EqualFold(field(f, 3), oldbase) {
				modified = set(3)
			}
		case "parent", "animroot":
			if oldbase != "" && strings.EqualFold(field(f, 2), oldbase) {
				modified = set(2)
			}
		}
		if modified {
			lines[idx] = strings.Join(f, " ")
		}
	}
	out = []byte(strings.Join(lines, "\n"))
	return out, !bytes.Equal(out, in)
}
```

- [ ] **Step 4: Run test to verify it passes**

Run: `go test ./internal/assets/mdl/`
Expected: PASS.

- [ ] **Step 5: Commit**

```bash
git add internal/assets/mdl/
git commit -m "feat(assets): pure-Go MDL model-name module"
```

---

## Task 2: Shared helpers + `Run` dispatch skeleton

**Files:**
- Create: `internal/assets/helpers.go`
- Create: `internal/assets/run.go`
- Test: `internal/assets/helpers_test.go`
- Test: `internal/assets/run_test.go`

**Interfaces:**
- Consumes: nothing.
- Produces:
  - `func Run(args []string, stdout, stderr io.Writer, getenv func(string) string) int`
  - Exit constants: `exitOK=0`, `exitFail=1`, `exitUsage=64`, `exitTool=70`.
  - `func walk(roots []string, exts map[string]bool, recursive bool) ([]string, error)` — files under each root whose lower-cased extension is in exts; a root that is itself a matching file is included; sorted, deduplicated.
  - `func look(candidates ...string) string` — first bare name found on PATH, or first candidate path that exists; "" if none.
  - `var runner = func(dir string, env []string, name string, args ...string) ([]byte, error)` — the single external-command indirection (combined output). Swapped in tests.

- [ ] **Step 1: Write the failing tests**

Create `internal/assets/helpers_test.go`:

```go
package assets

import (
	"os"
	"path/filepath"
	"testing"
)

func TestWalk(t *testing.T) {
	root := t.TempDir()
	must := func(rel string) {
		p := filepath.Join(root, rel)
		if err := os.MkdirAll(filepath.Dir(p), 0o755); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(p, []byte("x"), 0o644); err != nil {
			t.Fatal(err)
		}
	}
	must("a.MDL")
	must("sub/b.mdl")
	must("sub/c.txt")

	exts := map[string]bool{".mdl": true}
	got, err := walk([]string{root}, exts, true)
	if err != nil {
		t.Fatal(err)
	}
	if len(got) != 2 {
		t.Fatalf("recursive walk = %v, want 2 mdl files", got)
	}

	got, _ = walk([]string{root}, exts, false)
	if len(got) != 1 || filepath.Base(got[0]) != "a.MDL" {
		t.Fatalf("non-recursive walk = %v, want only a.MDL", got)
	}

	// A file argument that matches is included directly.
	got, _ = walk([]string{filepath.Join(root, "sub", "b.mdl")}, exts, true)
	if len(got) != 1 {
		t.Fatalf("file arg walk = %v, want the file itself", got)
	}
}

func TestLook(t *testing.T) {
	dir := t.TempDir()
	stub := filepath.Join(dir, "mytool")
	if err := os.WriteFile(stub, []byte("#!/bin/sh\n"), 0o755); err != nil {
		t.Fatal(err)
	}
	t.Setenv("PATH", dir)

	if got := look("nope-not-here", "mytool"); got == "" {
		t.Fatal("look should find mytool on PATH")
	}
	// Explicit existing path candidate.
	if got := look(stub); got != stub {
		t.Fatalf("look(%q) = %q, want the path itself", stub, got)
	}
	if got := look("definitely-absent-binary-xyz"); got != "" {
		t.Fatalf("look = %q, want empty", got)
	}
}
```

Create `internal/assets/run_test.go`:

```go
package assets

import (
	"bytes"
	"strings"
	"testing"
)

func env(string) string { return "" }

func TestRunNoArgsIsUsage(t *testing.T) {
	var out, errw bytes.Buffer
	if code := Run(nil, &out, &errw, env); code != exitUsage {
		t.Fatalf("no args exit = %d, want %d", code, exitUsage)
	}
	if !strings.Contains(errw.String(), "usage") {
		t.Fatalf("no args should print usage, got: %q", errw.String())
	}
}

func TestRunUnknownSubcommandIsUsage(t *testing.T) {
	var out, errw bytes.Buffer
	if code := Run([]string{"frobnicate"}, &out, &errw, env); code != exitUsage {
		t.Fatalf("unknown subcommand exit = %d, want %d", code, exitUsage)
	}
}
```

- [ ] **Step 2: Run tests to verify they fail**

Run: `go test ./internal/assets/`
Expected: FAIL — `assets` package has no source files yet.

- [ ] **Step 3: Write the helpers**

Create `internal/assets/helpers.go`:

```go
// Package assets is the crucible `assets` builder: NWN:EE model/texture tools
// that operate in place on a target directory. Mirrors internal/depot's
// Run(args, stdout, stderr, getenv) shape and bypasses the legacy internal/app
// surface entirely.
package assets

import (
	"os"
	"os/exec"
	"path/filepath"
	"sort"
	"strings"
)

// runner is the single external-command indirection so tests can observe and
// stub every engine / ImageMagick / upscaler invocation. dir is the working
// directory ("" = inherit); env replaces the child environment when non-nil.
var runner = func(dir string, env []string, name string, args ...string) ([]byte, error) {
	cmd := exec.Command(name, args...)
	cmd.Dir = dir
	if env != nil {
		cmd.Env = env
	}
	return cmd.CombinedOutput()
}

// walk collects files under each root whose lower-cased extension is in exts. A
// root that is itself a matching file is included. recursive controls descent
// into subdirectories. Results are sorted and deduplicated.
func walk(roots []string, exts map[string]bool, recursive bool) ([]string, error) {
	seen := map[string]bool{}
	var out []string
	add := func(p string) {
		if exts[strings.ToLower(filepath.Ext(p))] && !seen[p] {
			seen[p] = true
			out = append(out, p)
		}
	}
	for _, root := range roots {
		fi, err := os.Stat(root)
		if err != nil {
			return nil, err
		}
		if !fi.IsDir() {
			add(root)
			continue
		}
		err = filepath.WalkDir(root, func(p string, d os.DirEntry, err error) error {
			if err != nil {
				return err
			}
			if d.IsDir() {
				if !recursive && p != root {
					return filepath.SkipDir
				}
				return nil
			}
			add(p)
			return nil
		})
		if err != nil {
			return nil, err
		}
	}
	sort.Strings(out)
	return out, nil
}

// look returns the first bare name found on PATH, or the first candidate that
// is an existing path. Returns "" if none resolve.
func look(candidates ...string) string {
	for _, c := range candidates {
		if strings.ContainsRune(c, filepath.Separator) {
			if fi, err := os.Stat(c); err == nil && !fi.IsDir() {
				return c
			}
			continue
		}
		if p, err := exec.LookPath(c); err == nil {
			return p
		}
	}
	return ""
}
```

- [ ] **Step 4: Write the Run dispatch skeleton**

Create `internal/assets/run.go`:

```go
package assets

import (
	"fmt"
	"io"
)

const (
	exitOK    = 0
	exitFail  = 1  // problems found / per-file failures
	exitUsage = 64 // bad invocation / unknown subcommand / bad flags
	exitTool  = 70 // missing external tool / internal error
)

// Run executes an assets subcommand. args[0] is the subcommand; returns the
// process exit code.
func Run(args []string, stdout, stderr io.Writer, getenv func(string) string) int {
	if len(args) == 0 {
		printUsage(stderr)
		return exitUsage
	}
	rest := args[1:]
	switch args[0] {
	case "check-dupes":
		return runCheckDupes(rest, stdout, stderr)
	case "clean-dupes":
		return runCleanDupes(rest, stdout, stderr)
	case "check-mdl":
		return runCheckMDL(rest, stdout, stderr)
	case "fix-mdl":
		return runFixMDL(rest, stdout, stderr)
	case "convert":
		return runConvert(rest, stdout, stderr)
	case "upscale":
		return runUpscale(rest, stdout, stderr)
	case "compile":
		return runCompile(rest, stdout, stderr, getenv)
	default:
		fmt.Fprintf(stderr, "assets: unknown subcommand %q\n\n", args[0])
		printUsage(stderr)
		return exitUsage
	}
}

func printUsage(w io.Writer) {
	fmt.Fprint(w, `usage:
  assets compile      [--nwn INSTALL] [--non-recursive] <dir>...
  assets convert      [--to dds|png|tga] [--backend PATH] [--non-recursive] <dir>...
  assets upscale      [--scale N] [--backend PATH] [--non-recursive] <dir>...
  assets check-mdl    <path>...
  assets fix-mdl      [--dry-run] <path>...
  assets check-dupes  <dir>...
  assets clean-dupes  [--dry-run] <primary> <clean>
`)
}
```

Note: `run.go` references `runCheckDupes`, `runConvert`, etc. which do not exist yet. **The package will not compile until Task 3+ add them.** To keep this task independently green, add temporary stubs in `run.go` now and delete each as its real task lands:

```go
// --- temporary stubs; removed as each command task lands ---
func runCheckDupes(_ []string, _, _ io.Writer) int        { return exitTool }
func runCleanDupes(_ []string, _, _ io.Writer) int         { return exitTool }
func runCheckMDL(_ []string, _, _ io.Writer) int           { return exitTool }
func runFixMDL(_ []string, _, _ io.Writer) int             { return exitTool }
func runConvert(_ []string, _, _ io.Writer) int            { return exitTool }
func runUpscale(_ []string, _, _ io.Writer) int            { return exitTool }
func runCompile(_ []string, _, _ io.Writer, _ func(string) string) int { return exitTool }
```

- [ ] **Step 5: Run tests to verify they pass**

Run: `go test ./internal/assets/`
Expected: PASS.

- [ ] **Step 6: Commit**

```bash
git add internal/assets/helpers.go internal/assets/run.go internal/assets/helpers_test.go internal/assets/run_test.go
git commit -m "feat(assets): Run dispatch skeleton + walk/look/runner helpers"
```

---

## Task 3: Wire `assets` into the dispatch registry, shim, smoke, docs

**Files:**
- Modify: `internal/dispatch/dispatch.go` (Registry: add `assets` entry; `runBuilder`: extend the direct-delegate branch)
- Modify: `internal/dispatch/dispatch_test.go` (`TestCanonicalCommandSurface`, `TestRegistryCommandNamesAndAliasesAreUnambiguous`)
- Create: `cmd/crucible-assets/main.go`
- Modify: `scripts/crucible-smoke.sh`
- Modify: `docs/command-surface.md`

**Interfaces:**
- Consumes: `assets.Run` from Task 2.
- Produces: `crucible assets …` and `crucible-assets …` as a wired builder.

- [ ] **Step 1: Add the Registry entry**

In `internal/dispatch/dispatch.go`, add this builder to the `Registry` slice (place it after the `depot` entry). Every command needs `Name`, `Summary`, `Usage` (metadata test requires them); no `AppCommand` (assets bypasses legacy routing):

```go
	{
		Name:    "assets",
		Bin:     "crucible-assets",
		Summary: "compile/convert/upscale NWN assets + mdl/dupe integrity",
		Commands: []Command{
			{Name: "compile", Summary: "compile ASCII .mdl models to binary in place", Usage: "crucible assets compile [--nwn INSTALL] [--non-recursive] <dir>..."},
			{Name: "convert", Summary: "convert textures to/from NWN DDS (flips vertically)", Usage: "crucible assets convert [--to dds|png|tga] [--backend PATH] [--non-recursive] <dir>..."},
			{Name: "upscale", Summary: "upscale textures through an installed backend", Usage: "crucible assets upscale [--scale N] [--backend PATH] [--non-recursive] <dir>..."},
			{Name: "check-mdl", Summary: "report uncompiled ASCII .mdl and model-name mismatches", Usage: "crucible assets check-mdl <path>..."},
			{Name: "fix-mdl", Summary: "lowercase .mdl names and rewrite model identity to match", Usage: "crucible assets fix-mdl [--dry-run] <path>..."},
			{Name: "check-dupes", Summary: "report runtime-name (basename) collisions across dirs", Usage: "crucible assets check-dupes <dir>..."},
			{Name: "clean-dupes", Summary: "delete clean-tree files whose basename collides with primary", Usage: "crucible assets clean-dupes [--dry-run] <primary> <clean>"},
		},
		Wired: true,
	},
```

- [ ] **Step 2: Extend the direct-delegate branch**

In `internal/dispatch/dispatch.go`, add the `assets` import:

```go
	"git.westgate.pw/ShadowsOverWestgate/sow-tools/internal/assets"
```

Replace the depot special-case block in `runBuilder`:

```go
	if b.Name == "depot" && b.Wired {
		// depot parses its own subcommand (status/push/verify/get/pull) and
		// has its own richer exit contract (0/1/2/64/70), so it bypasses the
		// b.Commands/delegateLegacy routing entirely.
		return depot.Run(args, out, errw, os.Getenv)
	}
```

with:

```go
	if b.Wired {
		// depot and assets are self-contained builders: they parse their own
		// subcommands and own their exit contract, bypassing the
		// b.Commands/delegateLegacy legacy routing entirely.
		switch b.Name {
		case "depot":
			return depot.Run(args, out, errw, os.Getenv)
		case "assets":
			return assets.Run(args, out, errw, os.Getenv)
		}
	}
```

- [ ] **Step 3: Add the standalone shim**

Create `cmd/crucible-assets/main.go`:

```go
// Command crucible-assets is the standalone assets builder (equivalent to
// `crucible assets`). A single-token binary keeps consumer wrapper scripts simple.
package main

import (
	"os"

	"git.westgate.pw/ShadowsOverWestgate/sow-tools/internal/dispatch"
)

func main() { os.Exit(dispatch.RunBuilder("assets", os.Args[1:])) }
```

- [ ] **Step 4: Run the dispatch guard tests and watch them fail**

Run: `go test ./internal/dispatch/`
Expected: FAIL. `TestCanonicalCommandSurface` fatals with `unexpected builder "assets"` (the new builder is not in its `want` map), and `TestRegistryCommandNamesAndAliasesAreUnambiguous` errors that `assets` commands have an empty `AppCommand`. These guard tests must be updated to admit the new self-contained builder.

- [ ] **Step 5: Update the dispatch guard tests**

In `internal/dispatch/dispatch_test.go`, extend the `want` map in `TestCanonicalCommandSurface` to add:

```go
		"assets": {"compile", "convert", "upscale", "check-mdl", "fix-mdl", "check-dupes", "clean-dupes"},
```

In `TestRegistryCommandNamesAndAliasesAreUnambiguous`, change the AppCommand exemption so `assets` (like `depot`) is not required to carry an `AppCommand`:

```go
			requireAppCommand := builder.Name != "depot" && builder.Name != "assets"
```

Run: `go test ./internal/dispatch/`
Expected: PASS.

- [ ] **Step 6: Add `assets` to the smoke wired list**

In `scripts/crucible-smoke.sh`, change:

```bash
wired=(depot hak module topdata wiki)
```

to:

```bash
wired=(assets depot hak module topdata wiki)
```

- [ ] **Step 7: Add the seven doc rows**

In `docs/command-surface.md`, under the `## Visible commands` table (after the last row), add:

```markdown
| `assets` | `compile` | Compile ASCII `.mdl` models to binary in place. |
| `assets` | `convert` | Convert textures to/from NWN DDS (flips vertically). |
| `assets` | `upscale` | Upscale textures through an installed backend. |
| `assets` | `check-mdl` | Report uncompiled ASCII `.mdl` and model-name mismatches. |
| `assets` | `fix-mdl` | Lowercase `.mdl` names and rewrite model identity to match. |
| `assets` | `check-dupes` | Report runtime-name (basename) collisions across dirs. |
| `assets` | `clean-dupes` | Delete clean-tree files whose basename collides with primary. |
```

- [ ] **Step 8: Build every package**

Run: `go build ./...`
Expected: clean build (the new `cmd/crucible-assets` and the dispatch changes compile).

- [ ] **Step 9: Run the smoke test**

Run: `make smoke`
Expected: output ends with `smoke ok: 0 unwired fail closed (70), 6 wired delegate to nwn-tool logic` (assets `--help` exits 0; no-subcommand exits 64, not 70).

- [ ] **Step 10: Commit**

```bash
git add internal/dispatch/ cmd/crucible-assets/ scripts/crucible-smoke.sh docs/command-surface.md
git commit -m "feat(assets): wire builder into dispatch, shim, smoke, docs"
```

---

## Task 4: `check-dupes` + `clean-dupes`

**Files:**
- Create: `internal/assets/dupes.go`
- Test: `internal/assets/dupes_test.go`
- Modify: `internal/assets/run.go` (remove the two dupes stubs)

**Interfaces:**
- Consumes: `exitOK`/`exitFail`/`exitUsage`, `walk` — not needed here (dupes walk *all* files, not by extension); uses its own full-tree scan.
- Produces: `func runCheckDupes(args []string, stdout, stderr io.Writer) int`, `func runCleanDupes(args []string, stdout, stderr io.Writer) int`.

Ports `check-duplicate-names.sh` (directory mode only) and `clean-duplicate-names.sh`. NWN packs hak entries by basename, so files at different paths with the same lower-cased basename silently clobber.

- [ ] **Step 1: Write the failing tests**

Create `internal/assets/dupes_test.go`:

```go
package assets

import (
	"bytes"
	"os"
	"path/filepath"
	"testing"
)

func touch(t *testing.T, path string) {
	t.Helper()
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(path, []byte("x"), 0o644); err != nil {
		t.Fatal(err)
	}
}

func TestCheckDupes(t *testing.T) {
	root := t.TempDir()
	touch(t, filepath.Join(root, "tex", "Foo.tga"))
	touch(t, filepath.Join(root, "plc", "foo.tga")) // basename collision (case-insensitive)

	var out, errw bytes.Buffer
	if code := runCheckDupes([]string{root}, &out, &errw); code != exitFail {
		t.Fatalf("collision exit = %d, want %d\n%s", code, exitFail, errw.String())
	}

	clean := t.TempDir()
	touch(t, filepath.Join(clean, "a.tga"))
	touch(t, filepath.Join(clean, "sub", "b.tga"))
	out.Reset()
	errw.Reset()
	if code := runCheckDupes([]string{clean}, &out, &errw); code != exitOK {
		t.Fatalf("no-collision exit = %d, want %d\n%s", code, exitOK, errw.String())
	}
}

func TestCleanDupes(t *testing.T) {
	primary := t.TempDir()
	clean := t.TempDir()
	touch(t, filepath.Join(primary, "keep.tga"))
	collide := filepath.Join(clean, "sub", "Keep.tga")
	survive := filepath.Join(clean, "unique.tga")
	touch(t, collide)
	touch(t, survive)

	// dry-run removes nothing.
	var out, errw bytes.Buffer
	if code := runCleanDupes([]string{"--dry-run", primary, clean}, &out, &errw); code != exitOK {
		t.Fatalf("dry-run exit = %d\n%s", code, errw.String())
	}
	if _, err := os.Stat(collide); err != nil {
		t.Fatal("dry-run deleted a file")
	}

	// real run deletes the collision, keeps the unique file.
	out.Reset()
	errw.Reset()
	if code := runCleanDupes([]string{primary, clean}, &out, &errw); code != exitOK {
		t.Fatalf("clean exit = %d\n%s", code, errw.String())
	}
	if _, err := os.Stat(collide); !os.IsNotExist(err) {
		t.Fatal("collision file was not deleted")
	}
	if _, err := os.Stat(survive); err != nil {
		t.Fatal("unique file was wrongly deleted")
	}
}

func TestCleanDupesRejectsOverlap(t *testing.T) {
	root := t.TempDir()
	sub := filepath.Join(root, "child")
	touch(t, filepath.Join(sub, "x.tga"))
	var out, errw bytes.Buffer
	if code := runCleanDupes([]string{root, sub}, &out, &errw); code != exitUsage {
		t.Fatalf("overlap exit = %d, want %d", code, exitUsage)
	}
}
```

- [ ] **Step 2: Run tests to verify they fail**

Run: `go test ./internal/assets/ -run Dupes`
Expected: FAIL — the stubs return `exitTool`.

- [ ] **Step 3: Implement dupes**

First remove the two stub lines `runCheckDupes` and `runCleanDupes` from `internal/assets/run.go`. Then create `internal/assets/dupes.go`:

```go
package assets

import (
	"flag"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"sort"
	"strings"
)

// allFiles returns every regular file under root (recursive).
func allFiles(root string) ([]string, error) {
	var out []string
	err := filepath.WalkDir(root, func(p string, d os.DirEntry, err error) error {
		if err != nil {
			return err
		}
		if !d.IsDir() {
			out = append(out, p)
		}
		return nil
	})
	sort.Strings(out)
	return out, err
}

// runCheckDupes reports files whose lower-cased basename collides across the
// given dirs. Read-only. Exit exitFail if any collision is found.
func runCheckDupes(args []string, stdout, stderr io.Writer) int {
	fs := flag.NewFlagSet("check-dupes", flag.ContinueOnError)
	fs.SetOutput(stderr)
	if err := fs.Parse(args); err != nil {
		return exitUsage
	}
	dirs := fs.Args()
	if len(dirs) == 0 {
		fmt.Fprintln(stderr, "assets check-dupes: usage: check-dupes <dir>...")
		return exitUsage
	}

	first := map[string]string{}
	fail := false
	for _, dir := range dirs {
		if fi, err := os.Stat(dir); err != nil || !fi.IsDir() {
			fmt.Fprintf(stderr, "assets check-dupes: no such dir: %s\n", dir)
			return exitUsage
		}
		files, err := allFiles(dir)
		if err != nil {
			fmt.Fprintln(stderr, "assets check-dupes:", err)
			return exitTool
		}
		for _, f := range files {
			key := strings.ToLower(filepath.Base(f))
			if prev, ok := first[key]; ok {
				fmt.Fprintf(stderr, "runtime-name collision: %s collides with %s\n", f, prev)
				fail = true
			} else {
				first[key] = f
			}
		}
	}
	if fail {
		fmt.Fprintln(stderr, "check-dupes: found runtime-name collision(s)")
		return exitFail
	}
	fmt.Fprintln(stdout, "check-dupes: OK")
	return exitOK
}

// runCleanDupes deletes files from <clean> whose lower-cased basename collides
// with any file in <primary>. Mutates only <clean>. Refuses to run if the two
// trees overlap.
func runCleanDupes(args []string, stdout, stderr io.Writer) int {
	fs := flag.NewFlagSet("clean-dupes", flag.ContinueOnError)
	fs.SetOutput(stderr)
	dryRun := fs.Bool("dry-run", false, "report deletions without removing")
	if err := fs.Parse(args); err != nil {
		return exitUsage
	}
	pos := fs.Args()
	if len(pos) != 2 {
		fmt.Fprintln(stderr, "assets clean-dupes: usage: clean-dupes [--dry-run] <primary> <clean>")
		return exitUsage
	}
	primary, clean := pos[0], pos[1]
	for _, d := range []string{primary, clean} {
		if fi, err := os.Stat(d); err != nil || !fi.IsDir() {
			fmt.Fprintf(stderr, "assets clean-dupes: no such dir: %s\n", d)
			return exitUsage
		}
	}
	primaryReal, err1 := filepath.EvalSymlinks(primary)
	cleanReal, err2 := filepath.EvalSymlinks(clean)
	if err1 != nil || err2 != nil {
		fmt.Fprintln(stderr, "assets clean-dupes: cannot resolve dirs")
		return exitTool
	}
	if overlaps(primaryReal, cleanReal) {
		fmt.Fprintln(stderr, "assets clean-dupes: primary and clean dirs must not overlap")
		return exitUsage
	}

	primaryFiles, err := allFiles(primary)
	if err != nil {
		fmt.Fprintln(stderr, "assets clean-dupes:", err)
		return exitTool
	}
	names := map[string]bool{}
	for _, f := range primaryFiles {
		names[strings.ToLower(filepath.Base(f))] = true
	}

	cleanFiles, err := allFiles(clean)
	if err != nil {
		fmt.Fprintln(stderr, "assets clean-dupes:", err)
		return exitTool
	}
	removed := 0
	for _, f := range cleanFiles {
		if !names[strings.ToLower(filepath.Base(f))] {
			continue
		}
		if *dryRun {
			fmt.Fprintf(stderr, "would delete clean-tree collision: %s\n", f)
		} else {
			if err := os.Remove(f); err != nil {
				fmt.Fprintln(stderr, "assets clean-dupes:", err)
				return exitTool
			}
			fmt.Fprintf(stderr, "deleted clean-tree collision: %s\n", f)
		}
		removed++
	}
	verb := "removed"
	if *dryRun {
		verb = "would remove"
	}
	fmt.Fprintf(stdout, "clean-dupes: %s %d file(s)\n", verb, removed)
	return exitOK
}

// overlaps reports whether either directory contains the other (or they are
// equal), using cleaned absolute-ish paths with a trailing separator.
func overlaps(a, b string) bool {
	as := a + string(filepath.Separator)
	bs := b + string(filepath.Separator)
	return strings.HasPrefix(as, bs) || strings.HasPrefix(bs, as)
}
```

- [ ] **Step 4: Run tests to verify they pass**

Run: `go test ./internal/assets/`
Expected: PASS.

- [ ] **Step 5: Commit**

```bash
git add internal/assets/dupes.go internal/assets/dupes_test.go internal/assets/run.go
git commit -m "feat(assets): check-dupes + clean-dupes basename-collision tools"
```

---

## Task 5: `check-mdl`

**Files:**
- Create: `internal/assets/checkmdl.go`
- Test: `internal/assets/checkmdl_test.go`
- Modify: `internal/assets/run.go` (remove the `runCheckMDL` stub)

**Interfaces:**
- Consumes: `internal/assets/mdl` (`IsASCII`, `ExpectedName`, `CheckNames`), `walk`, exit constants.
- Produces: `func runCheckMDL(args []string, stdout, stderr io.Writer) int`.

Read-only. Each `<path>` is a file or dir (recursed for `*.mdl`). Reports uncompiled ASCII models and every model-name mismatch. Exit `exitFail` if any is found.

- [ ] **Step 1: Write the failing test**

Create `internal/assets/checkmdl_test.go`:

```go
package assets

import (
	"bytes"
	"os"
	"path/filepath"
	"testing"
)

func TestCheckMDL(t *testing.T) {
	dir := t.TempDir()
	// Uncompiled ASCII model with a name mismatch.
	bad := filepath.Join(dir, "foo.mdl")
	if err := os.WriteFile(bad, []byte("newmodel wrong\nbeginmodelgeom wrong\nendmodelgeom wrong\ndonemodel wrong\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	var out, errw bytes.Buffer
	if code := runCheckMDL([]string{dir}, &out, &errw); code != exitFail {
		t.Fatalf("bad mdl exit = %d, want %d\n%s", code, exitFail, errw.String())
	}

	// A binary (compiled) model is fine.
	good := t.TempDir()
	if err := os.WriteFile(filepath.Join(good, "bar.mdl"), []byte("\x00\x00compiled binary blob"), 0o644); err != nil {
		t.Fatal(err)
	}
	out.Reset()
	errw.Reset()
	if code := runCheckMDL([]string{good}, &out, &errw); code != exitOK {
		t.Fatalf("binary mdl exit = %d, want %d\n%s", code, exitOK, errw.String())
	}
}
```

- [ ] **Step 2: Run test to verify it fails**

Run: `go test ./internal/assets/ -run CheckMDL`
Expected: FAIL — stub returns `exitTool`.

- [ ] **Step 3: Implement check-mdl**

Remove the `runCheckMDL` stub from `run.go`. Create `internal/assets/checkmdl.go`:

```go
package assets

import (
	"flag"
	"fmt"
	"io"

	"git.westgate.pw/ShadowsOverWestgate/sow-tools/internal/assets/mdl"
)

// mdlExt is the file set shared by the mdl commands.
var mdlExt = map[string]bool{".mdl": true}

// runCheckMDL reports uncompiled ASCII .mdl files and model-name mismatches.
// Read-only. Exit exitFail if any problem is found.
func runCheckMDL(args []string, stdout, stderr io.Writer) int {
	fs := flag.NewFlagSet("check-mdl", flag.ContinueOnError)
	fs.SetOutput(stderr)
	nonRecursive := fs.Bool("non-recursive", false, "do not descend into subdirectories")
	if err := fs.Parse(args); err != nil {
		return exitUsage
	}
	paths := fs.Args()
	if len(paths) == 0 {
		fmt.Fprintln(stderr, "assets check-mdl: usage: check-mdl <path>...")
		return exitUsage
	}

	files, err := walk(paths, mdlExt, !*nonRecursive)
	if err != nil {
		fmt.Fprintln(stderr, "assets check-mdl:", err)
		return exitUsage
	}

	fail := false
	for _, f := range files {
		ascii, err := mdl.IsASCII(f)
		if err != nil {
			fmt.Fprintln(stderr, "assets check-mdl:", err)
			return exitTool
		}
		if ascii {
			fmt.Fprintf(stderr, "uncompiled ascii mdl: %s\n", f)
			fail = true
		}
		mismatches, err := mdl.CheckNames(f)
		if err != nil {
			fmt.Fprintln(stderr, "assets check-mdl:", err)
			return exitTool
		}
		expected := mdl.ExpectedName(f)
		for _, m := range mismatches {
			if m.Line == 0 {
				fmt.Fprintf(stderr, "%s: mdl model-name mismatch: root node is %s, expected %s\n", f, m.Got, expected)
			} else {
				fmt.Fprintf(stderr, "%s: mdl model-name mismatch: line %d: %s is %s, expected %s\n", f, m.Line, m.What, m.Got, expected)
			}
			fail = true
		}
	}
	if fail {
		fmt.Fprintln(stderr, "check-mdl: found broken or uncompiled .mdl file(s)")
		return exitFail
	}
	fmt.Fprintln(stdout, "check-mdl: OK")
	return exitOK
}
```

- [ ] **Step 4: Run test to verify it passes**

Run: `go test ./internal/assets/`
Expected: PASS.

- [ ] **Step 5: Commit**

```bash
git add internal/assets/checkmdl.go internal/assets/checkmdl_test.go internal/assets/run.go
git commit -m "feat(assets): check-mdl uncompiled/name-mismatch report"
```

---

## Task 6: `fix-mdl`

**Files:**
- Create: `internal/assets/fixmdl.go`
- Test: `internal/assets/fixmdl_test.go`
- Modify: `internal/assets/run.go` (remove the `runFixMDL` stub)

**Interfaces:**
- Consumes: `internal/assets/mdl` (`ExpectedName`, `CheckNames`, `FixNames`, `IsASCII`), `walk`, `mdlExt`, exit constants.
- Produces: `func runFixMDL(args []string, stdout, stderr io.Writer) int`.

For each `*.mdl`: lowercase the filename if needed (abort that file on a case-collision), then for ASCII models with a name mismatch rewrite the identity in place. `--dry-run` touches nothing.

- [ ] **Step 1: Write the failing test**

Create `internal/assets/fixmdl_test.go`:

```go
package assets

import (
	"bytes"
	"os"
	"path/filepath"
	"testing"

	"git.westgate.pw/ShadowsOverWestgate/sow-tools/internal/assets/mdl"
)

func TestFixMDL(t *testing.T) {
	dir := t.TempDir()
	// Uppercase name + internal mismatch.
	upper := filepath.Join(dir, "Foo.MDL")
	body := "newmodel wrong\nbeginmodelgeom wrong\nendmodelgeom wrong\ndonemodel wrong\n"
	if err := os.WriteFile(upper, []byte(body), 0o644); err != nil {
		t.Fatal(err)
	}

	// dry-run: nothing changes on disk.
	var out, errw bytes.Buffer
	if code := runFixMDL([]string{"--dry-run", dir}, &out, &errw); code != exitOK {
		t.Fatalf("dry-run exit = %d\n%s", code, errw.String())
	}
	if _, err := os.Stat(upper); err != nil {
		t.Fatal("dry-run renamed a file")
	}

	// real run: file is lowercased and its identity rewritten to match.
	out.Reset()
	errw.Reset()
	if code := runFixMDL([]string{dir}, &out, &errw); code != exitOK {
		t.Fatalf("fix exit = %d\n%s", code, errw.String())
	}
	lowered := filepath.Join(dir, "foo.mdl")
	if _, err := os.Stat(lowered); err != nil {
		t.Fatalf("file was not lowercased: %v", err)
	}
	mismatches, err := mdl.CheckNames(lowered)
	if err != nil {
		t.Fatal(err)
	}
	if len(mismatches) != 0 {
		data, _ := os.ReadFile(lowered)
		t.Fatalf("model still has mismatches after fix: %+v\n%s", mismatches, data)
	}
}
```

- [ ] **Step 2: Run test to verify it fails**

Run: `go test ./internal/assets/ -run FixMDL`
Expected: FAIL — stub returns `exitTool`.

- [ ] **Step 3: Implement fix-mdl**

Remove the `runFixMDL` stub from `run.go`. Create `internal/assets/fixmdl.go`:

```go
package assets

import (
	"flag"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"

	"git.westgate.pw/ShadowsOverWestgate/sow-tools/internal/assets/mdl"
)

// runFixMDL lowercases .mdl filenames and rewrites ASCII model identity to
// match each file's stem. Binary models are skipped (the engine owns those).
func runFixMDL(args []string, stdout, stderr io.Writer) int {
	fs := flag.NewFlagSet("fix-mdl", flag.ContinueOnError)
	fs.SetOutput(stderr)
	dryRun := fs.Bool("dry-run", false, "report changes without touching disk")
	nonRecursive := fs.Bool("non-recursive", false, "do not descend into subdirectories")
	if err := fs.Parse(args); err != nil {
		return exitUsage
	}
	paths := fs.Args()
	if len(paths) == 0 {
		fmt.Fprintln(stderr, "assets fix-mdl: usage: fix-mdl [--dry-run] <path>...")
		return exitUsage
	}

	files, err := walk(paths, mdlExt, !*nonRecursive)
	if err != nil {
		fmt.Fprintln(stderr, "assets fix-mdl:", err)
		return exitUsage
	}

	changed := 0
	failed := false
	for _, f := range files {
		// 1. Lowercase the basename if needed.
		//
		// ponytail: 35k files are each read once here (CheckNames + the rewrite
		// on candidates). The shell reference batched an awk pass to avoid
		// per-file subprocess spawns; in Go a plain read is cheap, so the batch
		// is not worth porting. If profiling ever shows this hot, parallelize
		// the loop.
		lower := f
		if base := filepath.Base(f); base != strings.ToLower(base) {
			lower = filepath.Join(filepath.Dir(f), strings.ToLower(base))
			if _, err := os.Stat(lower); err == nil {
				fmt.Fprintf(stderr, "assets fix-mdl: lowercase collision: %s -> %s\n", f, lower)
				failed = true
				continue
			}
			if *dryRun {
				fmt.Fprintf(stdout, "would lowercase: %s -> %s\n", f, lower)
			} else {
				if err := os.Rename(f, lower); err != nil {
					fmt.Fprintf(stderr, "assets fix-mdl: failed to lowercase %s: %v\n", f, err)
					failed = true
					continue
				}
				fmt.Fprintf(stdout, "lowercased: %s -> %s\n", f, lower)
			}
			changed++
		}

		// 2. Rewrite model identity if the (lowercased) file has a mismatch.
		//    In dry-run the on-disk file is still the original path.
		readPath := lower
		if *dryRun && lower != f {
			readPath = f
		}
		data, err := os.ReadFile(readPath)
		if err != nil {
			fmt.Fprintln(stderr, "assets fix-mdl:", err)
			failed = true
			continue
		}
		out, wasChanged := mdl.FixNames(data, mdl.ExpectedName(lower))
		if !wasChanged {
			continue
		}
		if *dryRun {
			fmt.Fprintf(stdout, "would fix: %s\n", lower)
		} else {
			if err := os.WriteFile(lower, out, 0o644); err != nil {
				fmt.Fprintln(stderr, "assets fix-mdl:", err)
				failed = true
				continue
			}
			fmt.Fprintf(stdout, "fixed: %s\n", lower)
		}
		changed++
	}

	if changed == 0 {
		fmt.Fprintln(stdout, "no broken mdl model names found")
	}
	if failed {
		return exitFail
	}
	return exitOK
}
```

- [ ] **Step 4: Run test to verify it passes**

Run: `go test ./internal/assets/`
Expected: PASS.

- [ ] **Step 5: Commit**

```bash
git add internal/assets/fixmdl.go internal/assets/fixmdl_test.go internal/assets/run.go
git commit -m "feat(assets): fix-mdl lowercase + identity rewrite"
```

---

## Task 7: `convert`

**Files:**
- Create: `internal/assets/convert.go`
- Test: `internal/assets/convert_test.go`
- Modify: `internal/assets/run.go` (remove the `runConvert` stub)

**Interfaces:**
- Consumes: `walk`, `look`, `runner`, exit constants.
- Produces:
  - `func runConvert(args []string, stdout, stderr io.Writer) int`
  - `func ddsToPNG(magickBin, src, dst string) error` — decode DDS to PNG, flipping vertically once.
  - `func pngToDDS(magickBin, src, dst string) error` — encode PNG to DDS, flipping once, auto-selecting DXT1 (opaque) vs DXT5 (alpha). (Used by `upscale` in Task 8.)

Every conversion flips vertically exactly once (NWN convention). Backend is ImageMagick `magick`; `--backend` overrides. Missing backend → fail closed.

- [ ] **Step 1: Write the failing test**

Create `internal/assets/convert_test.go`. This is a real round-trip using `magick` (present in the dev shell); it skips if `magick` is absent:

```go
package assets

import (
	"bytes"
	"image"
	"image/color"
	"image/png"
	"os"
	"os/exec"
	"path/filepath"
	"testing"
)

// writeTestPNG writes a 4x4 image: top two rows red, bottom two rows blue.
func writeTestPNG(t *testing.T, path string) {
	t.Helper()
	img := image.NewRGBA(image.Rect(0, 0, 4, 4))
	for y := 0; y < 4; y++ {
		c := color.RGBA{255, 0, 0, 255} // red
		if y >= 2 {
			c = color.RGBA{0, 0, 255, 255} // blue
		}
		for x := 0; x < 4; x++ {
			img.Set(x, y, c)
		}
	}
	f, err := os.Create(path)
	if err != nil {
		t.Fatal(err)
	}
	defer f.Close()
	if err := png.Encode(f, img); err != nil {
		t.Fatal(err)
	}
}

func topRowIsBlue(t *testing.T, pngPath string) bool {
	t.Helper()
	f, err := os.Open(pngPath)
	if err != nil {
		t.Fatal(err)
	}
	defer f.Close()
	img, err := png.Decode(f)
	if err != nil {
		t.Fatal(err)
	}
	r, _, b, _ := img.At(0, 0).RGBA()
	return b > r // blue dominates the top-left after a flip
}

func TestConvertFlipsOnceAndRoundTrips(t *testing.T) {
	magick := look("magick")
	if magick == "" {
		t.Skip("magick not on PATH")
	}
	dir := t.TempDir()
	src := filepath.Join(dir, "tex.png")
	writeTestPNG(t, src)

	// Convert PNG -> DDS (in place: tex.png becomes tex.dds, original removed).
	var out, errw bytes.Buffer
	if code := runConvert([]string{"--to", "dds", dir}, &out, &errw); code != exitOK {
		t.Fatalf("to-dds exit = %d\n%s", code, errw.String())
	}
	dds := filepath.Join(dir, "tex.dds")
	if _, err := os.Stat(dds); err != nil {
		t.Fatalf("dds not produced: %v", err)
	}
	if _, err := os.Stat(src); !os.IsNotExist(err) {
		t.Fatal("source png was not replaced")
	}

	// Decode the DDS RAW (no extra flip) and confirm a single flip happened:
	// the source top row was red, so the DDS top row must now be blue.
	raw := filepath.Join(dir, "raw.png")
	if err := exec.Command(magick, dds, raw).Run(); err != nil {
		t.Fatalf("raw decode: %v", err)
	}
	if !topRowIsBlue(t, raw) {
		t.Fatal("expected the DDS to be vertically flipped vs the source")
	}

	// Convert DDS -> PNG (another flip). Result should match the original.
	out.Reset()
	errw.Reset()
	if code := runConvert([]string{"--to", "png", dir}, &out, &errw); code != exitOK {
		t.Fatalf("to-png exit = %d\n%s", code, errw.String())
	}
	restored := filepath.Join(dir, "tex.png")
	if topRowIsBlue(t, restored) {
		t.Fatal("round trip did not restore the original orientation")
	}
}

func TestConvertMissingBackendFailsClosed(t *testing.T) {
	dir := t.TempDir()
	writeTestPNG(t, filepath.Join(dir, "tex.png"))
	var out, errw bytes.Buffer
	code := runConvert([]string{"--backend", "/nonexistent/magick", dir}, &out, &errw)
	if code != exitTool {
		t.Fatalf("missing backend exit = %d, want %d", code, exitTool)
	}
}
```

- [ ] **Step 2: Run test to verify it fails**

Run: `go test ./internal/assets/ -run Convert`
Expected: FAIL — stub returns `exitTool` for the round-trip (and the missing-backend case happens to pass by luck; the round-trip is the real failure).

- [ ] **Step 3: Implement convert**

Remove the `runConvert` stub from `run.go`. Create `internal/assets/convert.go`:

```go
package assets

import (
	"flag"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
)

var textureExts = map[string]bool{".dds": true, ".png": true, ".tga": true}

// runConvert converts textures in place, flipping vertically exactly once per
// conversion. --to defaults to dds. Files already in the target format are
// skipped.
func runConvert(args []string, stdout, stderr io.Writer) int {
	fs := flag.NewFlagSet("convert", flag.ContinueOnError)
	fs.SetOutput(stderr)
	to := fs.String("to", "dds", "target format: dds|png|tga")
	backend := fs.String("backend", "magick", "ImageMagick-compatible binary")
	nonRecursive := fs.Bool("non-recursive", false, "do not descend into subdirectories")
	if err := fs.Parse(args); err != nil {
		return exitUsage
	}
	target := strings.ToLower(*to)
	if target != "dds" && target != "png" && target != "tga" {
		fmt.Fprintln(stderr, "assets convert: --to must be dds, png, or tga")
		return exitUsage
	}
	dirs := fs.Args()
	if len(dirs) == 0 {
		fmt.Fprintln(stderr, "assets convert: usage: convert [--to dds|png|tga] <dir>...")
		return exitUsage
	}

	magick := look(*backend)
	if magick == "" {
		fmt.Fprintf(stderr, "assets convert: backend %q not found — install ImageMagick (magick)\n", *backend)
		return exitTool
	}

	files, err := walk(dirs, textureExts, !*nonRecursive)
	if err != nil {
		fmt.Fprintln(stderr, "assets convert:", err)
		return exitUsage
	}

	targetExt := "." + target
	failed := false
	for _, src := range files {
		srcExt := strings.ToLower(filepath.Ext(src))
		if srcExt == targetExt {
			continue // already in the target format
		}
		dst := strings.TrimSuffix(src, filepath.Ext(src)) + targetExt
		var convErr error
		if target == "dds" {
			convErr = pngToDDS(magick, src, dst)
		} else {
			convErr = ddsToPNG(magick, src, dst) // works for any decodable source
		}
		if convErr != nil {
			fmt.Fprintf(stderr, "assets convert: %s: %v\n", src, convErr)
			failed = true
			continue
		}
		if dst != src {
			if err := os.Remove(src); err != nil {
				fmt.Fprintf(stderr, "assets convert: %s: %v\n", src, err)
				failed = true
			}
		}
	}
	if failed {
		return exitFail
	}
	return exitOK
}

// ddsToPNG decodes src to dst (PNG/TGA by dst's extension), flipping vertically
// once. The single flip is the defining NWN behavior.
func ddsToPNG(magickBin, src, dst string) error {
	if out, err := runner("", nil, magickBin, src, "-flip", dst); err != nil {
		return fmt.Errorf("magick: %v: %s", err, strings.TrimSpace(string(out)))
	}
	return nil
}

// pngToDDS encodes src to a DDS at dst, flipping vertically once and choosing
// DXT1 for opaque images, DXT5 for images with alpha.
func pngToDDS(magickBin, src, dst string) error {
	compression := "dxt1"
	if hasAlpha(magickBin, src) {
		compression = "dxt5"
	}
	// ponytail: mipmaps rely on magick's default full chain (NWN wants a
	// pyramid, which magick writes by default). Add `-define dds:mipmaps=N`
	// here if a specific count is ever required.
	out, err := runner("", nil, magickBin, src, "-flip",
		"-define", "dds:compression="+compression, dst)
	if err != nil {
		return fmt.Errorf("magick: %v: %s", err, strings.TrimSpace(string(out)))
	}
	return nil
}

// hasAlpha reports whether src has any non-opaque pixel, via `magick identify`.
// On any probe error it assumes alpha (DXT5), the safe/lossless-alpha default.
func hasAlpha(magickBin, src string) bool {
	out, err := runner("", nil, magickBin, "identify", "-format", "%[opaque]", src)
	if err != nil {
		return true
	}
	return !strings.EqualFold(strings.TrimSpace(string(out)), "true")
}
```

- [ ] **Step 4: Run test to verify it passes**

Run: `go test ./internal/assets/ -run Convert`
Expected: PASS (or SKIP if `magick` is absent — it is present in `nix develop`).

- [ ] **Step 5: Commit**

```bash
git add internal/assets/convert.go internal/assets/convert_test.go internal/assets/run.go
git commit -m "feat(assets): convert textures to/from NWN DDS with single flip"
```

---

## Task 8: `upscale`

**Files:**
- Create: `internal/assets/upscale.go`
- Test: `internal/assets/upscale_test.go`
- Modify: `internal/assets/run.go` (remove the `runUpscale` stub)

**Interfaces:**
- Consumes: `walk`, `look`, `runner`, `ddsToPNG`/`pngToDDS` (Task 7), `textureExts`, exit constants.
- Produces: `func runUpscale(args []string, stdout, stderr io.Writer) int`.

Backend discovery, first found wins: `upscayl-bin`, `upscayl`, `realesrgan-ncnn-vulkan`, `waifu2x-ncnn-vulkan`; `--backend` overrides. They share the ncnn-vulkan CLI shape `-i IN -o OUT -s SCALE`. PNG/TGA upscaled directly; DDS goes dds→png→upscale→dds so the flip stays correct (needs `magick` too). No backend → fail closed.

- [ ] **Step 1: Write the failing test**

Create `internal/assets/upscale_test.go`. It stubs `runner` so no real upscaler runs — the stub simulates the ncnn CLI by copying input to output:

```go
package assets

import (
	"bytes"
	"os"
	"path/filepath"
	"testing"
)

func TestUpscalePNGUsesBackend(t *testing.T) {
	// A fake backend binary on PATH so look() resolves it.
	binDir := t.TempDir()
	fake := filepath.Join(binDir, "upscayl-bin")
	if err := os.WriteFile(fake, []byte("#!/bin/sh\n"), 0o755); err != nil {
		t.Fatal(err)
	}
	t.Setenv("PATH", binDir)

	// Stub runner: emulate `-i in -o out -s scale` by copying in->out.
	orig := runner
	defer func() { runner = orig }()
	var gotScale string
	runner = func(dir string, env []string, name string, args ...string) ([]byte, error) {
		var in, out string
		for i := 0; i < len(args)-1; i++ {
			switch args[i] {
			case "-i":
				in = args[i+1]
			case "-o":
				out = args[i+1]
			case "-s":
				gotScale = args[i+1]
			}
		}
		data, err := os.ReadFile(in)
		if err != nil {
			return nil, err
		}
		return nil, os.WriteFile(out, data, 0o644)
	}

	dir := t.TempDir()
	src := filepath.Join(dir, "tex.png")
	if err := os.WriteFile(src, []byte("pngdata"), 0o644); err != nil {
		t.Fatal(err)
	}
	var stdout, stderr bytes.Buffer
	if code := runUpscale([]string{"--scale", "2", dir}, &stdout, &stderr); code != exitOK {
		t.Fatalf("upscale exit = %d\n%s", code, stderr.String())
	}
	if gotScale != "2" {
		t.Fatalf("scale passed to backend = %q, want 2", gotScale)
	}
	if data, _ := os.ReadFile(src); string(data) != "pngdata" {
		t.Fatalf("upscaled file content = %q, want the backend output", data)
	}
}

func TestUpscaleNoBackendFailsClosed(t *testing.T) {
	t.Setenv("PATH", t.TempDir()) // empty PATH: no backend resolvable
	dir := t.TempDir()
	if err := os.WriteFile(filepath.Join(dir, "tex.png"), []byte("x"), 0o644); err != nil {
		t.Fatal(err)
	}
	var stdout, stderr bytes.Buffer
	if code := runUpscale([]string{dir}, &stdout, &stderr); code != exitTool {
		t.Fatalf("no-backend exit = %d, want %d", code, exitTool)
	}
}
```

- [ ] **Step 2: Run test to verify it fails**

Run: `go test ./internal/assets/ -run Upscale`
Expected: FAIL — stub returns `exitTool`, so the first test's `exitOK` expectation fails.

- [ ] **Step 3: Implement upscale**

Remove the `runUpscale` stub from `run.go`. Create `internal/assets/upscale.go`:

```go
package assets

import (
	"flag"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strconv"
	"strings"
)

var upscaleBackends = []string{"upscayl-bin", "upscayl", "realesrgan-ncnn-vulkan", "waifu2x-ncnn-vulkan"}

// runUpscale upscales textures in place through an installed ncnn-vulkan
// backend. DDS inputs are bridged through PNG so the NWN flip stays correct.
func runUpscale(args []string, stdout, stderr io.Writer) int {
	fs := flag.NewFlagSet("upscale", flag.ContinueOnError)
	fs.SetOutput(stderr)
	scale := fs.Int("scale", 4, "upscale factor")
	backend := fs.String("backend", "", "override the upscaler binary")
	nonRecursive := fs.Bool("non-recursive", false, "do not descend into subdirectories")
	if err := fs.Parse(args); err != nil {
		return exitUsage
	}
	dirs := fs.Args()
	if len(dirs) == 0 {
		fmt.Fprintln(stderr, "assets upscale: usage: upscale [--scale N] <dir>...")
		return exitUsage
	}

	candidates := upscaleBackends
	if *backend != "" {
		candidates = []string{*backend}
	}
	tool := look(candidates...)
	if tool == "" {
		fmt.Fprintf(stderr, "assets upscale: no upscaler found — install one of: %s\n", strings.Join(upscaleBackends, ", "))
		return exitTool
	}

	files, err := walk(dirs, textureExts, !*nonRecursive)
	if err != nil {
		fmt.Fprintln(stderr, "assets upscale:", err)
		return exitUsage
	}

	// magick is only needed if a .dds input is present; resolve lazily.
	magick := ""
	failed := false
	for _, src := range files {
		var upErr error
		if strings.EqualFold(filepath.Ext(src), ".dds") {
			if magick == "" {
				if magick = look("magick"); magick == "" {
					fmt.Fprintln(stderr, "assets upscale: .dds input needs ImageMagick (magick) for the png bridge")
					return exitTool
				}
			}
			upErr = upscaleDDS(tool, magick, src, *scale)
		} else {
			upErr = upscaleImage(tool, src, src, *scale)
		}
		if upErr != nil {
			fmt.Fprintf(stderr, "assets upscale: %s: %v\n", src, upErr)
			failed = true
		}
	}
	if failed {
		return exitFail
	}
	return exitOK
}

// upscaleImage runs the ncnn-vulkan backend to upscale src into dst (may be the
// same path).
func upscaleImage(tool, src, dst string, scale int) error {
	tmp := dst + ".upscaled.png"
	out, err := runner("", nil, tool, "-i", src, "-o", tmp, "-s", strconv.Itoa(scale))
	if err != nil {
		return fmt.Errorf("%s: %v: %s", filepath.Base(tool), err, strings.TrimSpace(string(out)))
	}
	return os.Rename(tmp, dst)
}

// upscaleDDS bridges a DDS through PNG: dds->png (flip), upscale, png->dds
// (flip back), yielding a correctly-flipped upscaled DDS.
func upscaleDDS(tool, magick, src string, scale int) error {
	tmpPNG := src + ".bridge.png"
	if err := ddsToPNG(magick, src, tmpPNG); err != nil {
		return err
	}
	defer os.Remove(tmpPNG)
	if err := upscaleImage(tool, tmpPNG, tmpPNG, scale); err != nil {
		return err
	}
	return pngToDDS(magick, tmpPNG, src)
}
```

- [ ] **Step 4: Run test to verify it passes**

Run: `go test ./internal/assets/ -run Upscale`
Expected: PASS.

- [ ] **Step 5: Commit**

```bash
git add internal/assets/upscale.go internal/assets/upscale_test.go internal/assets/run.go
git commit -m "feat(assets): upscale via ncnn-vulkan backend with dds bridge"
```

---

## Task 9: `compile`

**Files:**
- Create: `internal/assets/compile.go`
- Test: `internal/assets/compile_test.go`
- Modify: `internal/assets/run.go` (remove the `runCompile` stub)

**Interfaces:**
- Consumes: `walk`, `look`, `runner`, `mdlExt`, `internal/assets/mdl` (`IsASCII`, `CheckNames`), exit constants, `getenv`.
- Produces: `func runCompile(args []string, stdout, stderr io.Writer, getenv func(string) string) int`.

Recursively find ASCII `.mdl` under each `<dir>` and compile each to binary in place, one at a time (the engine's `development/` and `modelcompiler/` folders are flat, single-slot). Discovers the `nwmain` binary on standard install roots; `--nwn` overrides. Wraps with `xvfb-run` when there is no `DISPLAY`. Aborts a model whose internal names differ (tells the user to run `fix-mdl`) — does not auto-fix. Binary models are reported and skipped, not errors.

- [ ] **Step 1: Write the failing test**

Create `internal/assets/compile_test.go`. It stubs `runner` to emulate the engine: on `compilemodel <stem>` it writes a binary artifact into the `modelcompiler/` dir. Discovery is satisfied via `--nwn` pointing at a fake binary:

```go
package assets

import (
	"bytes"
	"os"
	"path/filepath"
	"testing"
)

func TestCompileDrivesEngineAndReplacesInPlace(t *testing.T) {
	home := t.TempDir()
	userData := filepath.Join(home, ".local", "share", "Neverwinter Nights")
	dev := filepath.Join(userData, "development")
	mc := filepath.Join(userData, "modelcompiler")
	for _, d := range []string{dev, mc} {
		if err := os.MkdirAll(d, 0o755); err != nil {
			t.Fatal(err)
		}
	}
	// Fake nwmain binary for discovery via --nwn.
	binDir := t.TempDir()
	nwmain := filepath.Join(binDir, "nwmain-linux")
	if err := os.WriteFile(nwmain, []byte("#!/bin/sh\n"), 0o755); err != nil {
		t.Fatal(err)
	}

	getenv := func(k string) string {
		switch k {
		case "HOME":
			return home
		case "DISPLAY":
			return ":0" // pretend a display exists so no xvfb wrap is needed
		}
		return ""
	}

	// Stub the engine: writes a binary compiled model into modelcompiler/.
	orig := runner
	defer func() { runner = orig }()
	runner = func(dir string, env []string, name string, args ...string) ([]byte, error) {
		// args: compilemodel <stem>
		stem := args[len(args)-1]
		compiled := filepath.Join(mc, stem+".mdl")
		return nil, os.WriteFile(compiled, []byte("\x00\x00compiled"), 0o644)
	}

	// Source tree with one ASCII model whose names already match its stem.
	srcDir := t.TempDir()
	src := filepath.Join(srcDir, "foo.mdl")
	body := "newmodel foo\nbeginmodelgeom foo\n  node dummy foo\n    parent null\n  endnode\nendmodelgeom foo\ndonemodel foo\n"
	if err := os.WriteFile(src, []byte(body), 0o644); err != nil {
		t.Fatal(err)
	}

	var stdout, stderr bytes.Buffer
	code := runCompile([]string{"--nwn", nwmain, srcDir}, &stdout, &stderr, getenv)
	if code != exitOK {
		t.Fatalf("compile exit = %d\n%s", code, stderr.String())
	}
	// The source is now binary (the compiled artifact moved back over it).
	data, err := os.ReadFile(src)
	if err != nil {
		t.Fatalf("compiled model missing: %v", err)
	}
	if string(data) != "\x00\x00compiled" {
		t.Fatalf("source not replaced by compiled binary: %q", data)
	}
}

func TestCompileAbortsOnNameMismatch(t *testing.T) {
	home := t.TempDir()
	if err := os.MkdirAll(filepath.Join(home, ".local", "share", "Neverwinter Nights", "development"), 0o755); err != nil {
		t.Fatal(err)
	}
	binDir := t.TempDir()
	nwmain := filepath.Join(binDir, "nwmain-linux")
	if err := os.WriteFile(nwmain, []byte("#!/bin/sh\n"), 0o755); err != nil {
		t.Fatal(err)
	}
	getenv := func(k string) string {
		if k == "HOME" {
			return home
		}
		if k == "DISPLAY" {
			return ":0"
		}
		return ""
	}
	orig := runner
	defer func() { runner = orig }()
	engineCalled := false
	runner = func(string, []string, string, ...string) ([]byte, error) {
		engineCalled = true
		return nil, nil
	}

	srcDir := t.TempDir()
	// Internal name "wrong" != stem "foo": must abort before touching the engine.
	if err := os.WriteFile(filepath.Join(srcDir, "foo.mdl"),
		[]byte("newmodel wrong\ndonemodel wrong\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	var stdout, stderr bytes.Buffer
	if code := runCompile([]string{"--nwn", nwmain, srcDir}, &stdout, &stderr, getenv); code != exitFail {
		t.Fatalf("mismatch exit = %d, want %d", code, exitFail)
	}
	if engineCalled {
		t.Fatal("engine should not run for a name-mismatched model")
	}
}
```

- [ ] **Step 2: Run tests to verify they fail**

Run: `go test ./internal/assets/ -run Compile`
Expected: FAIL — stub returns `exitTool`.

- [ ] **Step 3: Implement compile**

Remove the `runCompile` stub from `run.go`. Create `internal/assets/compile.go`:

```go
package assets

import (
	"flag"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"

	"git.westgate.pw/ShadowsOverWestgate/sow-tools/internal/assets/mdl"
)

// runCompile compiles ASCII .mdl models to binary in place, one at a time (the
// engine's development/ and modelcompiler/ folders are flat, single-slot).
func runCompile(args []string, stdout, stderr io.Writer, getenv func(string) string) int {
	fs := flag.NewFlagSet("compile", flag.ContinueOnError)
	fs.SetOutput(stderr)
	nwn := fs.String("nwn", "", "path to the NWN install root or nwmain-linux binary")
	nonRecursive := fs.Bool("non-recursive", false, "do not descend into subdirectories")
	if err := fs.Parse(args); err != nil {
		return exitUsage
	}
	dirs := fs.Args()
	if len(dirs) == 0 {
		fmt.Fprintln(stderr, "assets compile: usage: compile [--nwn INSTALL] <dir>...")
		return exitUsage
	}

	home := getenv("HOME")
	userData := filepath.Join(home, ".local", "share", "Neverwinter Nights")
	dev := filepath.Join(userData, "development")
	mc := filepath.Join(userData, "modelcompiler")

	nwmain := findNWMain(*nwn, home)
	if nwmain == "" {
		fmt.Fprintln(stderr, "assets compile: nwmain-linux not found — pass --nwn <install> "+
			"(Steam/GOG/Beamdog install root or the nwmain-linux binary)")
		return exitTool
	}
	binDir := filepath.Dir(nwmain)

	// Headless wrap: no DISPLAY + xvfb-run present -> run under a virtual X.
	var wrap []string
	if getenv("DISPLAY") == "" {
		if xvfb := look("xvfb-run"); xvfb != "" {
			wrap = []string{xvfb, "-a", "--server-args=-screen 0 1024x768x24"}
		}
	}

	files, err := walk(dirs, mdlExt, !*nonRecursive)
	if err != nil {
		fmt.Fprintln(stderr, "assets compile:", err)
		return exitUsage
	}

	failed := false
	for _, src := range files {
		if err := compileOne(src, binDir, nwmain, dev, mc, wrap, userData, stdout, stderr); err != nil {
			fmt.Fprintf(stderr, "assets compile: %s: %v\n", src, err)
			failed = true
		}
	}
	if failed {
		return exitFail
	}
	return exitOK
}

// findNWMain resolves the nwmain-linux binary from --nwn or standard roots.
func findNWMain(override, home string) string {
	if override != "" {
		if fi, err := os.Stat(override); err == nil && !fi.IsDir() {
			return override
		}
		cand := filepath.Join(override, "bin", "linux-x86", "nwmain-linux")
		if fi, err := os.Stat(cand); err == nil && !fi.IsDir() {
			return cand
		}
		return ""
	}
	return look(
		filepath.Join(home, ".local/share/Steam/steamapps/common/Neverwinter Nights/bin/linux-x86/nwmain-linux"),
		filepath.Join(home, "GOG Games/Neverwinter Nights Enhanced Edition/game/bin/linux-x86/nwmain-linux"),
		filepath.Join(home, ".steam/steam/steamapps/common/Neverwinter Nights/bin/linux-x86/nwmain-linux"),
	)
}

// compileOne compiles a single model. Binary models are reported and skipped
// (not an error). A name-mismatched model is aborted with guidance.
func compileOne(src, binDir, nwmain, dev, mc string, wrap []string, userData string, stdout, stderr io.Writer) error {
	ascii, err := mdl.IsASCII(src)
	if err != nil {
		return err
	}
	if !ascii {
		fmt.Fprintf(stdout, "skip (already compiled): %s\n", src)
		return nil
	}
	mismatches, err := mdl.CheckNames(src)
	if err != nil {
		return err
	}
	if len(mismatches) > 0 {
		return fmt.Errorf("model names differ from the file stem; run `crucible assets fix-mdl` first")
	}

	stem := mdl.ExpectedNameStem(src)
	name := strings.ToLower(filepath.Base(src))
	devFile := filepath.Join(dev, name)
	// Collision guard: a pre-existing slot aborts before any mutation.
	if _, err := os.Stat(devFile); err == nil {
		return fmt.Errorf("development slot already occupied: %s", devFile)
	}

	data, err := os.ReadFile(src)
	if err != nil {
		return err
	}
	if err := os.WriteFile(devFile, data, 0o644); err != nil {
		return err
	}
	defer os.Remove(devFile)

	// Run the engine with cwd = the binary dir.
	cmd := append(append([]string{}, wrap...), nwmain, "compilemodel", stem)
	if out, err := runner(binDir, nil, cmd[0], cmd[1:]...); err != nil {
		printEngineLog(userData, stderr)
		return fmt.Errorf("engine: %v: %s", err, strings.TrimSpace(string(out)))
	}

	// Collect the compiled artifact from modelcompiler/ (match by stem, any case).
	compiled, err := findCompiled(mc, stem)
	if err != nil {
		printEngineLog(userData, stderr)
		return err
	}
	defer os.Remove(compiled)

	out, err := os.ReadFile(compiled)
	if err != nil {
		return err
	}
	// Move it back over the source path, lowercased.
	dst := filepath.Join(filepath.Dir(src), name)
	if err := os.WriteFile(dst, out, 0o644); err != nil {
		return err
	}
	if dst != src {
		_ = os.Remove(src)
	}
	fmt.Fprintf(stdout, "compiled: %s\n", dst)
	return nil
}

// findCompiled returns the modelcompiler/ artifact whose stem matches (case-
// insensitively).
func findCompiled(mc, stem string) (string, error) {
	entries, err := os.ReadDir(mc)
	if err != nil {
		return "", err
	}
	want := strings.ToLower(stem) + ".mdl"
	for _, e := range entries {
		if e.IsDir() {
			continue
		}
		if strings.ToLower(e.Name()) == want {
			return filepath.Join(mc, e.Name()), nil
		}
	}
	return "", fmt.Errorf("engine produced no compiled model for %q", stem)
}

// printEngineLog appends a short tail of the engine log as advisory diagnostics.
func printEngineLog(userData string, stderr io.Writer) {
	log := filepath.Join(userData, "logs", "nwengineLog.txt")
	data, err := os.ReadFile(log)
	if err != nil {
		return
	}
	lines := strings.Split(strings.TrimRight(string(data), "\n"), "\n")
	if len(lines) > 8 {
		lines = lines[len(lines)-8:]
	}
	fmt.Fprintf(stderr, "  engine log tail (%s):\n", log)
	for _, l := range lines {
		fmt.Fprintf(stderr, "    %s\n", l)
	}
}
```

The `mdl` package needs a stem accessor that is not path-suffixed. Add to `internal/assets/mdl/mdl.go`:

```go
// ExpectedNameStem is an alias of ExpectedName kept for call-site clarity where
// the value is used as the engine's model stem argument.
func ExpectedNameStem(path string) string { return ExpectedName(path) }
```

(Alternatively call `mdl.ExpectedName(src)` directly in `compileOne` and skip this alias — do whichever reads cleaner. If you skip the alias, replace `mdl.ExpectedNameStem(src)` with `mdl.ExpectedName(src)`.)

- [ ] **Step 4: Run tests to verify they pass**

Run: `go test ./internal/assets/ -run Compile`
Expected: PASS.

- [ ] **Step 5: Run the full package test + vet**

Run: `go test ./internal/assets/... && go vet ./internal/assets/...`
Expected: PASS, no vet complaints. Confirm every temporary stub has been deleted from `run.go` (grep for `exitTool }` one-liners).

- [ ] **Step 6: Commit**

```bash
git add internal/assets/compile.go internal/assets/compile_test.go internal/assets/mdl/mdl.go internal/assets/run.go
git commit -m "feat(assets): compile ASCII mdl via the NWN engine in place"
```

---

## Task 10: Full-suite verification

**Files:** none (verification only).

- [ ] **Step 1: Run the whole test suite**

Run: `make check`
Expected: `go vet ./...`, `go test ./...`, `shellcheck scripts/*.sh`, and `yamllint .gitea` all pass.

- [ ] **Step 2: Build every binary and smoke-test**

Run: `make smoke`
Expected: ends with `smoke ok: 0 unwired fail closed (70), 6 wired delegate to nwn-tool logic`.

- [ ] **Step 3: Exercise the real surface once by hand**

Run:

```bash
go run ./cmd/crucible assets --help
go run ./cmd/crucible assets check-dupes .
```

Expected: `--help` prints the seven-subcommand help and exits 0; `check-dupes .` prints either `check-dupes: OK` (exit 0) or collision lines (exit 1) — never the unwired exit-70 message.

- [ ] **Step 4: Commit any doc touch-ups** (only if Step 3 surfaced a wording fix)

```bash
git add -A
git commit -m "docs(assets): tidy help text"
```

---

## Task 11 (deferred, separate repo): `sow-assets-manifest` consumer migration

**This task lands as its own commit in `../sow-assets-manifest` *after* a `crucible` release that includes `assets` is available** — it is NOT part of this repo's commits. Listed here so it is not lost. Do it only once the release exists and `./crucible.sh` in that repo resolves the new version.

- Delete the three fully-folded driver scripts: `scripts/check-ascii-mdl.sh`, `scripts/fix-mdl-model-names.sh`, `scripts/clean-duplicate-names.sh`.
- Repoint the Makefile targets to the wrapper:
  - `check-mdl` → `./crucible.sh assets check-mdl …`
  - `fix-mdl` → `./crucible.sh assets fix-mdl [--dry-run] …`
  - `check-dupes` directory scan → `./crucible.sh assets check-dupes …` (the `check-duplicate-names.sh --manifests` line stays as-is)
  - `clean-dupes` → `./crucible.sh assets clean-dupes [--dry-run] <PRIMARY> <CLEAN>`
- **Keep for now** (retired in the depot-pipeline follow-up spec): `scripts/check-duplicate-names.sh` (only its `--manifests` mode), `scripts/mdl-scan.awk`, `scripts/mdl-name-lib.sh` (still sourced by `import.sh`'s batched pre-import gate).

---

## Self-Review

**Spec coverage** — every design section maps to a task:
- Seven commands → Tasks 4–9 (check-dupes/clean-dupes/check-mdl/fix-mdl/convert/upscale/compile).
- `internal/assets/run.go` + shared helpers → Task 2.
- `internal/assets/mdl` module → Task 1.
- `cmd/crucible-assets/main.go` + dispatch Registry + delegate branch → Task 3.
- `docs/command-surface.md` rows + smoke `assets` expectation → Task 3.
- Consumer migration → Task 11 (deferred, separate repo, as the spec dictates).
- Error handling (missing tool 70, per-file failures collected, report commands exit-on-find, usage 64) → encoded in each command's exit contract + Global Constraints.
- Testing section (flag/usage parsing, backend discovery on fabricated PATH, walk recursion, real magick round-trip asserting single flip, mdl fixtures, dupes trees + overlap guard + dry-run) → Tasks 1, 2, 4, 7, 8.

**Out of scope** (correctly deferred, not planned here): the `check-duplicate-names.sh --manifests` mode and the depot-interacting pipeline (`import.sh`/`sync-assets.sh`/`export.sh`) — both belong to `2026-07-12-crucible-depot-pipeline-migration-design.md`.

**Type consistency:** `runner(dir, env, name, args...)`, `walk(roots, exts, recursive)`, `look(candidates...)`, `ddsToPNG`/`pngToDDS(magickBin, src, dst)`, and `mdl.{IsASCII,ExpectedName,CheckNames,FixNames}` are used with identical signatures across every task that consumes them. Exit constants (`exitOK/exitFail/exitUsage/exitTool`) are defined once in Task 2 and reused.

**Simplifications deliberately taken** (per spec "Simplify" + ponytail, each marked in code): `convert` relies on magick's default DDS mipmap chain rather than a tuned count; `FixNames` rebuilds only changed lines with single spaces (matching the retiring awk); `fix-mdl` reads each file once rather than porting the awk batch. Each has a `ponytail:` comment naming the ceiling and upgrade path.