feat: wire TKG builder into worker pipeline + face-face edges

- Auto-run tkg_builder.py after face trace store + Qdrant sync + trace chunks
- Add face-face CO_OCCURS_WITH edges (two traces in same frame)
- docs: TKG integration report for M4

scripts/tkg_builder.py

@@ -365,6 +365,73 @@ def build_speaker_face_edges(cur, schema, file_uuid):
     return edge_count
 
 
+def build_face_face_edges(cur, schema, file_uuid):
+    """Build CO_OCCURS_WITH edges: face_trace ↔ face_trace in same frame"""
+    print("[TKG] Building face-face co-occurrence edges...")
+
+    cur.execute(
+        f"""
+        SELECT a.trace_id AS tid_a, b.trace_id AS tid_b,
+               a.frame_number, a.timestamp_secs,
+               a.x AS ax, a.y AS ay, a.width AS aw, a.height AS ah,
+               b.x AS bx, b.y AS by, b.width AS bw, b.height AS bh
+        FROM {schema}.face_detections a
+        JOIN {schema}.face_detections b
+          ON a.file_uuid = b.file_uuid
+         AND a.frame_number = b.frame_number
+         AND a.trace_id < b.trace_id
+        WHERE a.file_uuid = %s
+          AND a.trace_id IS NOT NULL
+          AND b.trace_id IS NOT NULL
+        ORDER BY a.frame_number
+        """,
+        (file_uuid,),
+    )
+    rows = cur.fetchall()
+    if not rows:
+        print("[TKG]   No face-face co-occurrences found")
+        return 0
+
+    # Deduplicate by pair (group all frames where same two traces co-occur)
+    pair_first = {}
+    pair_frames = {}
+    for tid_a, tid_b, frame, ts, ax, ay, aw, ah, bx, by, bw, bh in rows:
+        key = (min(tid_a, tid_b), max(tid_a, tid_b))
+        if key not in pair_first:
+            pair_first[key] = frame
+        pair_frames.setdefault(key, []).append(frame)
+
+    edge_count = 0
+    for (tid_a, tid_b), frames in pair_frames.items():
+        cur.execute(
+            f"SELECT id FROM {schema}.tkg_nodes WHERE file_uuid=%s AND node_type='face_trace' AND external_id=%s",
+            (file_uuid, f"trace_{tid_a}"),
+        )
+        n_a = cur.fetchone()
+        cur.execute(
+            f"SELECT id FROM {schema}.tkg_nodes WHERE file_uuid=%s AND node_type='face_trace' AND external_id=%s",
+            (file_uuid, f"trace_{tid_b}"),
+        )
+        n_b = cur.fetchone()
+        if not n_a or not n_b:
+            continue
+
+        distance_px = ((frames[0] - frames[0]) ** 2) ** 0.5  # placeholder
+        ensure_edge(
+            cur, schema, file_uuid,
+            "CO_OCCURS_WITH",
+            n_a[0], n_b[0],
+            {
+                "first_frame": int(frames[0]),
+                "frame_count": len(frames),
+            },
+        )
+        edge_count += 1
+
+    print(f"[TKG]   {edge_count} face-face co-occurrence edges created")
+    return edge_count
+
+
 def main():
     parser = argparse.ArgumentParser(description="Build Temporal Knowledge Graph")
     parser.add_argument("--file-uuid", required=True)
@@ -382,17 +449,19 @@ def main():
 
     e1 = build_co_occurrence_edges(cur, args.schema, args.file_uuid)
     e2 = build_speaker_face_edges(cur, args.schema, args.file_uuid)
+    e3 = build_face_face_edges(cur, args.schema, args.file_uuid)
 
     conn.commit()
     cur.close()
     conn.close()
 
-    print(f"\n[TKG] Complete: {n1+n2+n3} nodes, {e1+e2} edges")
+    print(f"\n[TKG] Complete: {n1+n2+n3} nodes, {e1+e2+e3} edges")
     print(f"  Face traces: {n1}")
     print(f"  Objects:     {n2}")
     print(f"  Speakers:    {n3}")
     print(f"  Co-occur:    {e1}")
     print(f"  Speaker-face:{e2}")
+    print(f"  Face-face:   {e3}")
 
 
 if __name__ == "__main__":