Add explicit force replacement workflow

internal/storage/backend.go

@@ -30,6 +30,7 @@ type Backend interface {
 	Walk(ctx context.Context, prefix string, opts WalkOptions, fn WalkFunc) error
 	HasAny(ctx context.Context, prefix string) (bool, error)
 	DeleteManagedBundle(ctx context.Context, bundlePath string, managedOutputPaths []string, opts DeleteOptions) error
+	DeletePrefix(ctx context.Context, prefix string, opts DeleteOptions) error
 }
 
 type WalkOptions struct {

internal/storage/errors.go

@@ -29,6 +29,7 @@ const (
 	OpWalk                = "walk"
 	OpHasAny              = "has any"
 	OpDeleteManagedBundle = "delete managed bundle"
+	OpDeletePrefix        = "delete prefix"
 	OpRegisterBackend     = "register backend"
 	OpOpenBackend         = "open backend"
 )

internal/storage/fake/backend.go

@@ -205,6 +205,41 @@ func (b *Backend) DeleteManagedBundle(ctx context.Context, bundlePath string, ma
 	return nil
 }
 
+func (b *Backend) DeletePrefix(ctx context.Context, prefix string, opts storage.DeleteOptions) error {
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+	if err := storage.ValidatePrefix(prefix); err != nil {
+		return err
+	}
+	if prefix != "" && !b.exists(prefix) && !b.hasChild(prefix) {
+		if opts.IgnoreMissing {
+			return nil
+		}
+		return storage.NewError(storage.OpDeletePrefix, backendName, prefix, storage.ErrNotFound, nil)
+	}
+	for path := range b.files {
+		if path == prefix || entryBelow(prefix, path) {
+			delete(b.files, path)
+		}
+	}
+	for path := range b.symlinks {
+		if path == prefix || entryBelow(prefix, path) {
+			delete(b.symlinks, path)
+		}
+	}
+	for path := range b.dirs {
+		if path != "" && (path == prefix || entryBelow(prefix, path)) {
+			delete(b.dirs, path)
+		}
+	}
+	if opts.PruneEmptyDirs {
+		b.pruneEmptyParents(parentOf(prefix))
+	}
+	b.dirs[""] = struct{}{}
+	return nil
+}
+
 func (b *Backend) ensureParents(path string) {
 	parent := parentOf(path)
 	for parent != "" {

internal/storage/fake/backend_test.go

@@ -140,6 +140,30 @@ func TestBackendManagedDeletion(t *testing.T) {
 	}
 }
 
+func TestBackendDeletePrefixStaysWithinPrefix(t *testing.T) {
+	backend := New()
+	mustWrite(t, backend, "bundle/report.md", "report")
+	mustWrite(t, backend, "bundle/nested/old.txt", "old")
+	mustWrite(t, backend, "bundle-sibling/keep.txt", "keep")
+	mustWrite(t, backend, "outside.txt", "outside")
+
+	if err := backend.DeletePrefix(context.Background(), "bundle", storage.DeleteOptions{IgnoreMissing: true, PruneEmptyDirs: true}); err != nil {
+		t.Fatalf("DeletePrefix() error = %v", err)
+	}
+	if _, err := backend.Stat(context.Background(), "bundle/report.md"); !storage.IsNotFound(err) {
+		t.Fatalf("deleted file stat error = %v, want not found", err)
+	}
+	if _, err := backend.Stat(context.Background(), "bundle/nested/old.txt"); !storage.IsNotFound(err) {
+		t.Fatalf("deleted nested file stat error = %v, want not found", err)
+	}
+	if _, err := backend.Stat(context.Background(), "bundle-sibling/keep.txt"); err != nil {
+		t.Fatalf("sibling stat error = %v", err)
+	}
+	if _, err := backend.Stat(context.Background(), "outside.txt"); err != nil {
+		t.Fatalf("outside stat error = %v", err)
+	}
+}
+
 func TestBackendHasAnyAndWalkStop(t *testing.T) {
 	backend := New()
 	found, err := backend.HasAny(context.Background(), "missing")

internal/storage/path_test.go

@@ -206,3 +206,7 @@ func (b walkBackend) HasAny(context.Context, string) (bool, error) {
 func (b walkBackend) DeleteManagedBundle(context.Context, string, []string, DeleteOptions) error {
 	return nil
 }
+
+func (b walkBackend) DeletePrefix(context.Context, string, DeleteOptions) error {
+	return nil
+}