feat(topdata): materialize Git-LFS asset bytes inside Crucible before packing

Adds materializeAssetLFS + hasLFSPointerStubs helpers to top_package.go.
Called at the top of packageBuiltTopData so bare CI checkouts never ship
~130-byte LFS pointer stubs. Opt-out via CRUCIBLE_SKIP_LFS env or the new
--skip-lfs flag on build-topdata / build-top-package.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/topdata/lfs_materialize_test.go

@@ -0,0 +1,29 @@
+package topdata
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestHasLFSPointerStubsDetectsStub(t *testing.T) {
+	root := t.TempDir()
+	if err := os.MkdirAll(filepath.Join(root, "a"), 0o755); err != nil {
+		t.Fatalf("mkdir: %v", err)
+	}
+	stub := "version https://git-lfs.github.com/spec/v1\noid sha256:abc\nsize 12345\n"
+	writeFile(t, filepath.Join(root, "a", "model.mdl"), stub)
+	writeFile(t, filepath.Join(root, "a", "real.txt"), "not a pointer, real bytes here")
+
+	if !hasLFSPointerStubs(root) {
+		t.Fatal("expected stub detection to be true")
+	}
+}
+
+func TestHasLFSPointerStubsNoStub(t *testing.T) {
+	root := t.TempDir()
+	writeFile(t, filepath.Join(root, "real.mdl"), "binary-ish content without a pointer header")
+	if hasLFSPointerStubs(root) {
+		t.Fatal("expected no stub detected")
+	}
+}

internal/topdata/top_package.go

@@ -1,6 +1,7 @@
 package topdata
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"io"
@@ -75,6 +76,7 @@ func BuildAndPackage(p *project.Project, progress func(string)) (PackageResult,
 type BuildAndPackageOptions struct {
 	Force     bool
 	BuildWiki bool
+	SkipLFS   bool
 }
 
 func BuildAndPackageWithOptions(p *project.Project, opts BuildAndPackageOptions, progress func(string)) (PackageResult, error) {
@@ -123,6 +125,9 @@ func packageBuiltTopData(p *project.Project, nativeResult BuildResult, progress
 	if progress == nil {
 		progress = func(string) {}
 	}
+	if err := materializeAssetLFS(p, progress); err != nil {
+		return PackageResult{}, err
+	}
 	outputHAK := p.TopDataPackageHAKPath()
 	outputTLK := p.TopDataPackageTLKPath()
 
@@ -711,3 +716,80 @@ func countCompiledFiles(dir, extension string) (int, time.Time, error) {
 	}
 	return count, oldest, nil
 }
+
+// materializeAssetLFS ensures the topdata asset tree holds real bytes, not
+// Git-LFS pointer stubs, before the hak is packed. A bare CI checkout does not
+// smudge LFS, so a direct Crucible build would otherwise ship ~130-byte stubs.
+// It uses the clone's own credentials (R1) and hard-fails if stubs survive the
+// pull. Set CRUCIBLE_SKIP_LFS=1 to opt out (maintain-tree regenerates the data/
+// tree and discards the package, so it must not hard-depend on LFS).
+func materializeAssetLFS(p *project.Project, progress func(string)) error {
+	if progress == nil {
+		progress = func(string) {}
+	}
+	assetsDir := filepath.Join(p.TopDataSourceDir(), "assets")
+	info, err := os.Stat(assetsDir)
+	if err != nil || !info.IsDir() {
+		return nil // no asset tree to materialize
+	}
+	if !hasLFSPointerStubs(assetsDir) {
+		return nil // already real bytes (or repo does not use LFS)
+	}
+	if isTruthyEnv(os.Getenv("CRUCIBLE_SKIP_LFS")) {
+		progress("CRUCIBLE_SKIP_LFS set: leaving Git-LFS pointer stubs unmaterialized (package will be discarded)")
+		return nil
+	}
+	if _, err := gitOutput(p.Root, "lfs", "version"); err != nil {
+		return fmt.Errorf("asset tree has Git-LFS pointer stubs but git-lfs is unavailable; install git-lfs or enter the nix devshell: %w", err)
+	}
+	progress("Materializing Git-LFS assets (git lfs pull)...")
+	// A fresh clone may lack the lfs smudge/clean filters; install them locally
+	// first (scoped to this repo's .git/config, no host mutation). Idempotent.
+	if _, err := gitOutput(p.Root, "lfs", "install", "--local"); err != nil {
+		return fmt.Errorf("git lfs install --local failed: %w", err)
+	}
+	if _, err := gitOutput(p.Root, "lfs", "pull"); err != nil {
+		return fmt.Errorf("git lfs pull failed: %w", err)
+	}
+	if hasLFSPointerStubs(assetsDir) {
+		return fmt.Errorf("refusing to build from pointer stubs: Git-LFS pointer stubs remain under %s after git lfs pull", assetsDir)
+	}
+	return nil
+}
+
+// hasLFSPointerStubs reports whether any small text file under root is a Git-LFS
+// pointer. Real assets are larger than any pointer stub, so the size gate keeps
+// this cheap on a tree of binaries.
+func hasLFSPointerStubs(root string) bool {
+	found := false
+	_ = filepath.WalkDir(root, func(path string, d os.DirEntry, err error) error {
+		if err != nil || d.IsDir() || found {
+			return nil
+		}
+		info, ierr := d.Info()
+		if ierr != nil || info.Size() == 0 || info.Size() > 1024 {
+			return nil
+		}
+		f, oerr := os.Open(path)
+		if oerr != nil {
+			return nil
+		}
+		defer f.Close()
+		buf := make([]byte, 256)
+		n, _ := f.Read(buf)
+		if bytes.Contains(buf[:n], []byte("git-lfs.github.com/spec/v1")) {
+			found = true
+		}
+		return nil
+	})
+	return found
+}
+
+func isTruthyEnv(v string) bool {
+	switch strings.TrimSpace(strings.ToLower(v)) {
+	case "1", "true", "yes", "on":
+		return true
+	default:
+		return false
+	}
+}