fix: increase WebSocket pub-sub timeout from 60s to 180s

LLM responses can take >60s (especially with local models). The
WebSocket listener was timing out before the response arrived,
causing agent replies to appear in logs but not in the chat UI.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/gateway/gateway/channels/web.py

@@ -58,7 +58,7 @@ logger = logging.getLogger(__name__)
 web_chat_router = APIRouter(tags=["web-chat"])
 
 # Timeout for waiting for an agent response via Redis pub-sub (seconds)
-_RESPONSE_TIMEOUT_SECONDS = 60
+_RESPONSE_TIMEOUT_SECONDS = 180
 
 
 def normalize_web_event(event: dict[str, Any]) -> KonstructMessage: