fix(agent-zero): queue expiry detection in adapter

Zulip event queues expire after ~600s of inactivity. The adapter now
detects 400/BAD_EVENT_QUEUE_ID responses and auto-reconnects instead of
silently returning empty results.

agent-zero-zulip/src/agent_zero_zulip/adapter.py

@@ -189,13 +189,18 @@ class AgentZeroZulipAdapter:
             await asyncio.sleep(DEFAULT_POLL_INTERVAL)
     
     async def _fetch_events(self) -> list:
-        """Fetch events from Zulip queue."""
-        resp = await self._api_call("GET", "/api/v1/events", params={
+        """Fetch events from Zulip queue. Raises on BAD_EVENT_QUEUE_ID."""
+        resp, status = await self._api_call("GET", "/api/v1/events", params={
             "queue_id": self._queue_id,
             "last_event_id": str(self._last_event_id),
             "dont_block": "true",
-        })
-        if resp is None:
+        }, return_status=True)
+        
+        # Detect queue expiry
+        if status == 400:
+            raise RuntimeError("BAD_EVENT_QUEUE_ID: queue expired")
+        
+        if not resp:
             return []
         
         events = resp.get("events", [])
@@ -365,10 +370,14 @@ class AgentZeroZulipAdapter:
     # ── Zulip API ──
     
     async def _api_call(self, method: str, path: str, 
-                        data: dict = None, params: dict = None) -> Optional[dict]:
-        """Make Zulip API call."""
+                        data: dict = None, params: dict = None,
+                        return_status: bool = False) -> Any:
+        """Make Zulip API call.
+        
+        Returns: dict response body, or if return_status=True returns (dict, int)
+        """
         if not self._http_client:
-            return None
+            return (None, 0) if return_status else None
         
         url = f"{self._site}{path}"
         headers = {"Authorization": self._auth_header}
@@ -381,16 +390,17 @@ class AgentZeroZulipAdapter:
             elif method == "PATCH":
                 resp = await self._http_client.patch(url, data=data, headers=headers)
             else:
-                return None
+                return (None, 0) if return_status else None
             
             if resp.status_code >= 400:
                 logger.debug(f"API {method} {path}: {resp.status_code}")
-                return None
+                return (None, resp.status_code) if return_status else None
             
-            return resp.json()
+            body = resp.json()
+            return (body, resp.status_code) if return_status else body
         except Exception as e:
             logger.debug(f"API error {method} {path}: {e}")
-            return None
+            return (None, 0) if return_status else None
     
     async def _send_msg(self, msg_type: str, to: str, content: str) -> Optional[int]:
         """Send a message to Zulip."""