fix: record and require the walk identity backend

recognization/code/record.py

@@ -15,7 +15,8 @@ Layout:
 
     DIR/<session>/000123.jpg          the frame, exactly as the client sent it
     DIR/<session>/index.jsonl         one line per frame:
-        {"frame": 123, "path": "...", "at": 1699..., "summary": {...},
+        {"frame": 123, "path": "...", "at": 1699..., "identity_backend": "gallery",
+         "summary": {...},
          "tracks": [{"box": [...], "identity": {...}, "tag": {...}}]}
 
 Frames are written at most every `every` processed frames (default 3) so a long
@@ -35,10 +36,17 @@ from typing import Any, Dict, List, Optional
 class FrameRecorder:
     """Write frames and their results to disk, for labelling later."""
 
-    def __init__(self, root: str, every: int = 3, max_frames_per_session: int = 4000) -> None:
+    def __init__(
+        self,
+        root: str,
+        every: int = 3,
+        max_frames_per_session: int = 4000,
+        identity_backend: Optional[str] = None,
+    ) -> None:
         self.root = root
         self.every = max(1, int(every))
         self.max_frames_per_session = int(max_frames_per_session)
+        self.identity_backend = (identity_backend or "").strip().lower() or None
         self._lock = threading.Lock()
         self._counts: Dict[str, int] = {}
         self._written: Dict[str, int] = {}
@@ -86,6 +94,8 @@ class FrameRecorder:
             "summary": result.get("summary"),
             "tracks": tracks,
         }
+        if self.identity_backend:
+            line["identity_backend"] = self.identity_backend
         try:
             with open(os.path.join(directory, "index.jsonl"), "a", encoding="utf-8") as handle:
                 handle.write(json.dumps(line, ensure_ascii=False) + "\n")