crucible depot: Increment 1 core (status/push/verify/get/pull + local/cdn/bunny backends) (#30)

Implements Increment 1 of `docs/superpowers/specs/2026-07-04-crucible-depot-core-design.md`: a new stdlib-only `internal/depot` package wired into the dispatcher.

- `crucible depot status|push|verify|get|pull` with backends `local`/`cdn`/`bunny`; exit contract `0` clean / `1` drift / `2` unconfirmed-only / `64` usage / `70` internal.
- Presence is always probed against the real target (IPv4 1-byte range GET; HEAD is banned with a regression-tripwire test). `unconfirmed` is a distinct state, never collapsed into `missing`.
- No prompting anywhere: missing `BUNNY_STORAGE_*` env fails closed (read path included), enforced by a no-stdin test.
- Uploads: probe-then-PUT with `Checksum: <UPPER-sha>`; read/write key split (`BUNNY_STORAGE_READ_PASSWORD` falls back to `BUNNY_STORAGE_PASSWORD`).
- Field-driven fix included: per-probe transient retry (curl `--retry 2` equivalent) — without it a real 1490-blob CDN sweep reported 1222 false-unconfirmed; with it, 1490/1490 present in 74s, exit 0.
- Registry: depot `Wired: true`, joins the interactive menu; stale "(SeaweedFS)" wording removed.

Tests: unit + httptest fake-Bunny (probe sequence, Checksum header, key split, 428 throttling → exit 2) + local→bunny integration (drift → push → clean → idempotent no-second-PUT; incremental pull). `make check` green.

**Merge ordering:** this merges FIRST; the companion `sow-assets-manifest#crucible-depot-cutover` PR needs its flake input bumped to include this.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: #30
Reviewed-by: xtul <mpiasecki720@protonmail.com>
Co-authored-by: vickydotbat <vickydotbat@tutamail.com>
Co-committed-by: vickydotbat <vickydotbat@tutamail.com>

internal/depot/local_test.go

@@ -0,0 +1,139 @@
+package depot
+
+import (
+	"bytes"
+	"context"
+	"crypto/sha256"
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestLocalRoundTrip(t *testing.T) {
+	tmpDir := t.TempDir()
+	backend := &LocalBackend{Root: tmpDir}
+
+	// Generate test data
+	testData := []byte("hello world")
+	testSHA := fmt.Sprintf("%x", sha256.Sum256(testData))
+
+	// Create source file
+	srcFile := filepath.Join(tmpDir, "source.txt")
+	if err := os.WriteFile(srcFile, testData, 0644); err != nil {
+		t.Fatalf("failed to create source file: %v", err)
+	}
+
+	// Put
+	ctx := context.Background()
+	if err := backend.Put(ctx, testSHA, srcFile); err != nil {
+		t.Fatalf("Put failed: %v", err)
+	}
+
+	// Probe should be Present
+	state, transient, err := backend.Probe(ctx, testSHA)
+	if err != nil {
+		t.Fatalf("Probe failed: %v", err)
+	}
+	if state != Present {
+		t.Fatalf("expected Present, got %v", state)
+	}
+	if transient {
+		t.Fatalf("local backend should never be transient")
+	}
+
+	// Get
+	destFile := filepath.Join(tmpDir, "dest.txt")
+	if err := backend.Get(ctx, testSHA, destFile); err != nil {
+		t.Fatalf("Get failed: %v", err)
+	}
+
+	// Verify bytes match
+	gotData, err := os.ReadFile(destFile)
+	if err != nil {
+		t.Fatalf("failed to read dest file: %v", err)
+	}
+	if !bytes.Equal(gotData, testData) {
+		t.Fatalf("data mismatch: want %s, got %s", testData, gotData)
+	}
+}
+
+func TestLocalProbeAbsent(t *testing.T) {
+	tmpDir := t.TempDir()
+	backend := &LocalBackend{Root: tmpDir}
+
+	ctx := context.Background()
+	state, transient, err := backend.Probe(ctx, "0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d")
+	if err != nil {
+		t.Fatalf("Probe should not error on missing blob: %v", err)
+	}
+	if state != Absent {
+		t.Fatalf("expected Absent, got %v", state)
+	}
+	if transient {
+		t.Fatalf("local backend should never be transient")
+	}
+}
+
+func TestLocalGetHashMismatch(t *testing.T) {
+	tmpDir := t.TempDir()
+	backend := &LocalBackend{Root: tmpDir}
+
+	// Create a corrupt blob at the expected path
+	sha := "0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d"
+	blobKey := BlobKey(sha)
+	blobPath := filepath.Join(tmpDir, blobKey)
+
+	if err := os.MkdirAll(filepath.Dir(blobPath), 0755); err != nil {
+		t.Fatalf("failed to create blob dir: %v", err)
+	}
+	if err := os.WriteFile(blobPath, []byte("wrong data"), 0644); err != nil {
+		t.Fatalf("failed to create blob file: %v", err)
+	}
+
+	// Get should error
+	ctx := context.Background()
+	destFile := filepath.Join(tmpDir, "dest.txt")
+	err := backend.Get(ctx, sha, destFile)
+	if err == nil {
+		t.Fatalf("Get should error on hash mismatch")
+	}
+
+	// Destination file should not exist
+	_, err = os.Stat(destFile)
+	if !os.IsNotExist(err) {
+		t.Fatalf("dest file should not exist after Get error: %v", err)
+	}
+}
+
+func TestLocalPutIdempotent(t *testing.T) {
+	tmpDir := t.TempDir()
+	backend := &LocalBackend{Root: tmpDir}
+
+	testData := []byte("hello world")
+	testSHA := fmt.Sprintf("%x", sha256.Sum256(testData))
+
+	srcFile := filepath.Join(tmpDir, "source.txt")
+	if err := os.WriteFile(srcFile, testData, 0644); err != nil {
+		t.Fatalf("failed to create source file: %v", err)
+	}
+
+	ctx := context.Background()
+
+	// Put twice
+	if err := backend.Put(ctx, testSHA, srcFile); err != nil {
+		t.Fatalf("first Put failed: %v", err)
+	}
+	if err := backend.Put(ctx, testSHA, srcFile); err != nil {
+		t.Fatalf("second Put failed: %v", err)
+	}
+
+	// Verify blob exists
+	state, _, err := backend.Probe(ctx, testSHA)
+	if err != nil {
+		t.Fatalf("Probe failed: %v", err)
+	}
+	if state != Present {
+		t.Fatalf("expected Present after Put, got %v", state)
+	}
+}