🐛(agents) hide agent and fix egress end when agent disabled

Fix the error created by trying to close agent when it is
disabled.
Make the agent hidden so users do not see it.

It makes the diarization invisible for users.

src/agents/metadata_extractor.py

@@ -271,6 +271,11 @@ if __name__ == "__main__":
             entrypoint_fnc=entrypoint,
             request_fnc=handle_job_request,
             agent_name=AGENT_NAME,
-            permissions=WorkerPermissions(),
+            permissions=WorkerPermissions(
+                can_publish=False,
+                can_publish_data=False,
+                can_subscribe=True,
+                hidden=True,
+            ),
         )
     )

src/backend/core/recording/services/recording_events.py

@@ -139,6 +139,10 @@ class RecordingEventsService:
         service = MetadataService()
         rec_id = recording.id
         room_id = recording.room_id
+        creator_id = get_recording_creator_id(recording)
+        if not FeatureFlag.flag_is_active("metadata_agent", distinct_id=creator_id):
+            logger.info("Metadata agent disabled by PostHog flag for id=%s", creator_id)
+            return
 
         def _stop():
             try: