don't let a lost object enter a zone

When the detector lost an object, the tracker kept it at its last box and every held frame still counted toward the zone's inertia. A car detected in a zone once or twice as it drove out of view could reach an inertia of 8 and be marked as entering, which sent it to GenAI and any other required zones check even though Review never showed the zone. Inertia and loitering still count on frames without a detection, but an object can only newly enter a zone on a frame where it was actually detected.

frigate/track/tracked_object.py

@@ -186,6 +186,7 @@ class TrackedObject:
         # check zones
         current_zones = []
         bottom_center = (obj_data["centroid"][0], obj_data["box"][3])
+        detected = obj_data["frame_time"] == current_frame_time
         in_loitering_zone = False
         in_speed_zone = False
 
@@ -275,11 +276,13 @@ class TrackedObject:
 
                         loitering_score = self.zone_loitering.get(name, 0) + 1
 
-                        # loitering time is configured as seconds, convert to count of frames
+                        # loitering time is configured as seconds, convert to count of frames.
+                        # a lost object keeps counting but can't newly enter a zone
+                        # until it is detected again
                         if loitering_score >= (
                             self.camera_config.zones[name].loitering_time
                             * self.camera_config.detect.fps
-                        ):
+                        ) and (detected or name in self.current_zones):
                             current_zones.append(name)
 
                             if name not in self.entered_zones: