```

refactor: improve agent notification types and fix activity curator

- Convert agent notifications to discriminated union (session/permission/status)
- Fix activity curator to properly handle typed session updates
- Serialize Date objects in AgentInfo for JSON compatibility
- Use activity curator for title generation context
- Reduce console.error to console.warn for non-critical WebSocket errors
- Improve spacing in agent stream views
- Delay title generation until 15+ updates available
```

packages/app/src/hooks/use-websocket.ts

@@ -48,7 +48,7 @@ export function useWebSocket(url: string, conversationId?: string | null): UseWe
       };
 
       ws.onerror = (error) => {
-        console.error('[WS] Error:', error);
+        console.warn('[WS] Error:', error);
       };
 
       ws.onmessage = (event) => {
@@ -87,7 +87,7 @@ export function useWebSocket(url: string, conversationId?: string | null): UseWe
 
       wsRef.current = ws;
     } catch (err) {
-      console.error('[WS] Failed to create WebSocket:', err);
+      console.warn('[WS] Failed to create WebSocket:', err);
     }
   }, [url, conversationId]);