fixed issues from opencode agent

internal/domain/oci/registry.go

@@ -27,7 +27,7 @@ type Registry struct {
 // New creates a Registry rooted at ociRoot, creating the directory tree if needed.
 func New(ociRoot string) (*Registry, error) {
 	for _, sub := range []string{"blobs/sha256", "uploads"} {
-		if err := os.MkdirAll(filepath.Join(ociRoot, sub), 0755); err != nil {
+		if err := os.MkdirAll(filepath.Join(ociRoot, sub), 0700); err != nil {
 			return nil, fmt.Errorf("oci: init storage %s: %w", sub, err)
 		}
 	}
@@ -174,7 +174,7 @@ func (r *Registry) FinishUpload(uploadID, clientDigest string) (digest string, s
 // new total offset.
 func (r *Registry) AppendUpload(uploadID string, src io.Reader) (newOffset int64, err error) {
 	path := r.UploadPath(uploadID)
-	f, err := os.OpenFile(path, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
+	f, err := os.OpenFile(path, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0600)
 	if err != nil {
 		return 0, fmt.Errorf("oci: open upload for append: %w", err)
 	}
@@ -291,9 +291,10 @@ func digestHex(digest string) (string, error) {
 	return h, nil
 }
 
-// sanitiseID strips any path separators from an upload ID.
+// sanitiseID returns only the last path component of an upload ID,
+// preventing any path traversal regardless of encoding.
 func sanitiseID(id string) string {
-	return strings.NewReplacer("/", "", "\\", "", "..", "").Replace(id)
+	return filepath.Base(id)
 }
 
 // ParseOCIPath extracts the image name and the operation kind from a path