refactor: extract locked filing block to keep mine_convos under C901

Adding the per-file lock + double-checked file_already_mined() in the
previous commit pushed mine_convos cyclomatic complexity from 25 to 26,
just over ruff's max-complexity threshold. Hoist the locked critical
section into _file_chunks_locked() so the outer loop stays within
budget. No behavior change.

mempalace/convo_miner.py

@@ -272,6 +272,47 @@ def scan_convos(convo_dir: str) -> list:
 # =============================================================================
 
 
+def _file_chunks_locked(collection, source_file, chunks, wing, room, agent, extract_mode):
+    """Acquire the per-file lock, double-check mined status, and upsert chunks.
+
+    Returns (drawers_added, room_counts_delta, skipped).
+    """
+    room_counts_delta: dict = defaultdict(int)
+    drawers_added = 0
+    with mine_lock(source_file):
+        # Re-check after lock — another agent may have just finished this file
+        if file_already_mined(collection, source_file):
+            return 0, room_counts_delta, True
+
+        for chunk in chunks:
+            chunk_room = chunk.get("memory_type", room) if extract_mode == "general" else room
+            if extract_mode == "general":
+                room_counts_delta[chunk_room] += 1
+            drawer_id = f"drawer_{wing}_{chunk_room}_{hashlib.sha256((source_file + str(chunk['chunk_index'])).encode()).hexdigest()[:24]}"
+            try:
+                collection.upsert(
+                    documents=[chunk["content"]],
+                    ids=[drawer_id],
+                    metadatas=[
+                        {
+                            "wing": wing,
+                            "room": chunk_room,
+                            "source_file": source_file,
+                            "chunk_index": chunk["chunk_index"],
+                            "added_by": agent,
+                            "filed_at": datetime.now().isoformat(),
+                            "ingest_mode": "convos",
+                            "extract_mode": extract_mode,
+                        }
+                    ],
+                )
+                drawers_added += 1
+            except Exception as e:
+                if "already exists" not in str(e).lower():
+                    raise
+    return drawers_added, room_counts_delta, False
+
+
 def mine_convos(
     convo_dir: str,
     palace_path: str,
@@ -376,39 +417,14 @@ def mine_convos(
             room_counts[room] += 1
 
         # File each chunk — lock to prevent concurrent agents duplicating
-        drawers_added = 0
+        drawers_added, room_delta, skipped = _file_chunks_locked(
-        with mine_lock(source_file):
+            collection, source_file, chunks, wing, room, agent, extract_mode
-            # Re-check after lock — another agent may have just finished this file
+        )
-            if file_already_mined(collection, source_file):
+        if skipped:
-                files_skipped += 1
+            files_skipped += 1
-                continue
+            continue
-
+        for r, n in room_delta.items():
-            for chunk in chunks:
+            room_counts[r] += n
-                chunk_room = chunk.get("memory_type", room) if extract_mode == "general" else room
-                if extract_mode == "general":
-                    room_counts[chunk_room] += 1
-                drawer_id = f"drawer_{wing}_{chunk_room}_{hashlib.sha256((source_file + str(chunk['chunk_index'])).encode()).hexdigest()[:24]}"
-                try:
-                    collection.upsert(
-                        documents=[chunk["content"]],
-                        ids=[drawer_id],
-                        metadatas=[
-                            {
-                                "wing": wing,
-                                "room": chunk_room,
-                                "source_file": source_file,
-                                "chunk_index": chunk["chunk_index"],
-                                "added_by": agent,
-                                "filed_at": datetime.now().isoformat(),
-                                "ingest_mode": "convos",
-                                "extract_mode": extract_mode,
-                            }
-                        ],
-                    )
-                    drawers_added += 1
-                except Exception as e:
-                    if "already exists" not in str(e).lower():
-                        raise
 
         total_drawers += drawers_added
         print(f"  ✓ [{i:4}/{len(files)}] {filepath.name[:50]:50} +{drawers_added}")