Clarify artifact root symlink behavior

internal/artifact/reader.go

@@ -158,14 +158,15 @@ func (r *restrictedFileReader) Read(ctx context.Context, ref domain.ArtifactRef)
 		return nil, ErrMissingFilePath
 	}
 
-	path, err := r.resolve(ref.URI)
+	path, err := r.resolveLexicalPath(ref.URI)
 	if err != nil {
 		return nil, err
 	}
 	return readFileArtifactWithLimit(path, r.maxBytes)
 }
 
-func (r *restrictedFileReader) resolve(rawPath string) (string, error) {
+// resolveLexicalPath checks cleaned path containment without resolving symlinks.
+func (r *restrictedFileReader) resolveLexicalPath(rawPath string) (string, error) {
 	cleanPath := filepath.Clean(strings.TrimSpace(rawPath))
 	var candidate string
 	if filepath.IsAbs(cleanPath) {