feat: room broadcast — say command delivers to all occupants in room

- say <message> now queues room_broadcast events on other sessions
- New GET /bridge/room_events/{user_id} endpoint (drain-on-read)
- WS connections receive real-time room broadcasts
- 5 new tests: broadcast, no-echo, room isolation, drain, 404
- Total tests: 27 (all passing)

nexus/multi_user_bridge.py

@@ -110,6 +110,7 @@ class UserSession:
     room: str = "The Tower"
     message_history: list[dict] = field(default_factory=list)
     ws_connections: list = field(default_factory=list)
+    room_events: list[dict] = field(default_factory=list)
     crisis_state: CrisisState = field(default_factory=CrisisState)
     created_at: float = field(default_factory=time.time)
     last_active: float = field(default_factory=time.time)
@@ -227,6 +228,7 @@ class MultiUserBridge:
         self._app.router.add_post("/bridge/chat", self.handle_chat)
         self._app.router.add_get("/bridge/sessions", self.handle_sessions)
         self._app.router.add_get("/bridge/health", self.handle_health)
+        self._app.router.add_get("/bridge/room_events/{user_id}", self.handle_room_events)
         self._app.router.add_get("/bridge/ws/{user_id}", self.handle_ws)
         return self._app
 
@@ -244,6 +246,20 @@ class MultiUserBridge:
             "total": self.sessions.active_count,
         })
 
+    async def handle_room_events(self, request: web.Request) -> web.Response:
+        """GET /bridge/room_events/{user_id} — Drain pending room events for a user."""
+        user_id = request.match_info["user_id"]
+        session = self.sessions.get(user_id)
+        if not session:
+            return web.json_response({"error": "session not found"}, status=404)
+        events = list(session.room_events)
+        session.room_events.clear()
+        return web.json_response({
+            "user_id": user_id,
+            "events": events,
+            "count": len(events),
+        })
+
     async def handle_chat(self, request: web.Request) -> web.Response:
         """
         POST /bridge/chat
@@ -294,6 +310,13 @@ class MultiUserBridge:
         }
         await self._broadcast_to_user(session, ws_event)
 
+        # Deliver room events to other users' WS connections (non-destructive)
+        for other_session in self.sessions._sessions.values():
+            if other_session.user_id != user_id and other_session.room_events:
+                for event in other_session.room_events:
+                    if event.get("from_user") == user_id:
+                        await self._broadcast_to_user(other_session, event)
+
         return web.json_response({
             "response": full_response,
             "user_id": user_id,
@@ -386,7 +409,21 @@ class MultiUserBridge:
 
         if msg_lower.startswith("say "):
             speech = message[4:]
-            # Broadcast to room occupants (non-WS for now)
+            # Broadcast to other occupants in same room
+            occupants = self.sessions.get_room_occupants(session.room)
+            others = [o for o in occupants if o != session.user_id]
+            if others:
+                broadcast = {
+                    "type": "room_broadcast",
+                    "from_user": session.user_id,
+                    "from_username": session.username,
+                    "room": session.room,
+                    "message": f'{session.username} says: "{speech}"',
+                }
+                for other_id in others:
+                    other_session = self.sessions.get(other_id)
+                    if other_session:
+                        other_session.room_events.append(broadcast)
             return f'You say: "{speech}"'
 
         if msg_lower == "who":