Improved perfs

internal/storage/store.go

@@ -22,9 +22,11 @@ type InterfaceMeta struct {
 	Version int    `json:"version"`
 }
 
-// Store persists interface definitions as XML files under {storageDir}/interfaces/.
+// Store persists interface definitions as XML files under {storageDir}/interfaces/
+// and workspace-level JSON blobs directly in {storageDir}.
 type Store struct {
-	dir string
+	rootDir string // {storageDir} — for workspace-level files (groups.json, etc.)
+	dir     string // {storageDir}/interfaces
 }
 
 // New opens (and creates, if needed) the storage directory.
@@ -33,7 +35,22 @@ func New(storageDir string) (*Store, error) {
 	if err := os.MkdirAll(dir, 0o755); err != nil {
 		return nil, fmt.Errorf("create interfaces dir: %w", err)
 	}
-	return &Store{dir: dir}, nil
+	return &Store{rootDir: storageDir, dir: dir}, nil
+}
+
+// ReadGroups returns the raw JSON array of group tree nodes.
+// Returns an empty JSON array if no groups have been saved yet.
+func (s *Store) ReadGroups() ([]byte, error) {
+	data, err := os.ReadFile(filepath.Join(s.rootDir, "groups.json"))
+	if errors.Is(err, os.ErrNotExist) {
+		return []byte("[]"), nil
+	}
+	return data, err
+}
+
+// WriteGroups persists the group tree. data must be a valid JSON array.
+func (s *Store) WriteGroups(data []byte) error {
+	return os.WriteFile(filepath.Join(s.rootDir, "groups.json"), data, 0o644)
 }
 
 // validateID returns an error if id could be used for path traversal or is