fix(edge): identity-aware GHOST dedup keyed on track_id (FIX 4)

edge/engine.py keyed the ghost cooldown as
(GHOST, round(x), round(y)) — purely spatial, ignoring track identity.
Two distinct workers collapsing at ~the same pixel within the cooldown
window would suppress each other's ghost event, potentially masking a
second CRITICAL incident.

edge/detectors/ghost.py GhostIncidentDetector.update now includes the
candidate's track_id in each emitted dict. edge/engine.py keys the
cooldown as (EventType.GHOST, track_id) and sets the emitted Event's
track_id accordingly, matching how FALL/NO_MOTION/IMMOBILITY/zone events
are already keyed per-track.

Tests: tests/test_ghost.py asserts ghosts[0]["track_id"] == 1 on the
existing reappear-timeout test.

edge/detectors/ghost.py

@@ -42,7 +42,7 @@ class GhostIncidentDetector:
         out = []
         for tid, (spatial, state, _height, lost_at) in list(self._candidates.items()):
             if now - lost_at >= self.cfg.reappear_s:
-                out.append({"spatial": spatial, "last_state": state,
+                out.append({"track_id": tid, "spatial": spatial, "last_state": state,
                             "waited_s": round(now - lost_at, 1)})
                 self._candidates.pop(tid, None)
         return out

edge/engine.py

@@ -67,9 +67,10 @@ class EventEngine:
                     events.append(self._mk(etype, now, tr.track_id, zone_id=hit["zone_id"]))
 
         for g in self.ghost.update(active_tracks, now):
-            key = (EventType.GHOST, round(g["spatial"][0]), round(g["spatial"][1]))
+            key = (EventType.GHOST, g["track_id"])
             if self._allow(key, now):
-                events.append(self._mk(EventType.GHOST, now, spatial=g["spatial"],
+                events.append(self._mk(EventType.GHOST, now, track_id=g["track_id"],
+                                       spatial=g["spatial"],
                                        metrics={"last_state": g["last_state"],
                                                 "waited_s": g["waited_s"]}))
         return events

tests/test_ghost.py

@@ -16,6 +16,7 @@ def test_lost_dangerous_track_becomes_ghost_after_wait():
     assert len(ghosts) == 1
     assert ghosts[0]["last_state"] == "FALLEN"
     assert ghosts[0]["spatial"] == (110.0, 130.0)  # bbox 중심
+    assert ghosts[0]["track_id"] == 1
 
 def test_non_dangerous_lost_track_is_ignored():
     d = GhostIncidentDetector(GhostConfig(reappear_s=1.0))