feat(collector): brain event 중계 추가 — Watcher 이벤트를 Gateway로 전달

- collector.py: _forward_events_loop — BrainEvent를 JSON으로 serialize하여 /api/event POST
- gateway.py: /api/event 엔드포인트 — 수신한 이벤트를 bot event_queue에 주입
- main.py: event_queue를 CollectorBridge에 전달

이제 task.md, implementation_plan, walkthrough 변경사항이 Collector→Gateway→Discord 경로로 전달됨

collector.py

@@ -18,6 +18,7 @@ from pathlib import Path
 
 from bridge import LocalTransport, RemoteTransport
 from config import Config
+from watcher import BrainEvent, EventType
 
 logger = logging.getLogger(__name__)
 
@@ -31,10 +32,12 @@ class CollectorBridge:
     3. Polls Gateway for commands → writes to local commands/
     """
 
-    def __init__(self, local: LocalTransport, remote: RemoteTransport, project_name: str):
+    def __init__(self, local: LocalTransport, remote: RemoteTransport,
+                 project_name: str, event_queue: asyncio.Queue | None = None):
         self.local = local
         self.remote = remote
         self.project_name = project_name
+        self.event_queue = event_queue
         self._forwarded_pending: set[str] = set()  # already forwarded request IDs
         self._poll_interval = 3  # seconds
         self._running = False
@@ -43,11 +46,14 @@ class CollectorBridge:
         """Start the Collector polling loops."""
         self._running = True
         logger.info(f"[COLLECTOR] started for project={self.project_name}")
-        await asyncio.gather(
+        tasks = [
             self._forward_pending_loop(),
             self._poll_responses_loop(),
             self._poll_commands_loop(),
-        )
+        ]
+        if self.event_queue:
+            tasks.append(self._forward_events_loop())
+        await asyncio.gather(*tasks)
 
     async def stop(self):
         """Stop the Collector."""
@@ -125,3 +131,28 @@ class CollectorBridge:
                 logger.error(f"[COLLECTOR] poll_commands error: {e}")
 
             await asyncio.sleep(self._poll_interval)
+
+    # ─── Forward brain events → Gateway ───
+
+    async def _forward_events_loop(self):
+        """Read BrainEvents from Watcher queue and POST to Gateway."""
+        while self._running:
+            try:
+                event: BrainEvent = await asyncio.wait_for(
+                    self.event_queue.get(), timeout=5.0
+                )
+                # Serialize event to JSON
+                event_data = {
+                    "event_type": event.event_type.value,
+                    "conversation_id": event.conversation_id,
+                    "file_name": event.file_name,
+                    "file_path": str(event.file_path) if event.file_path else "",
+                    "content": event.content,
+                    "timestamp": event.timestamp,
+                }
+                self.remote._request("POST", "/api/event", event_data)
+                logger.info(f"[COLLECTOR] → Gateway: event {event.event_type.value} {event.file_name}")
+            except asyncio.TimeoutError:
+                continue
+            except Exception as e:
+                logger.error(f"[COLLECTOR] forward_event error: {e}")