feat: event-driven ui updates

.living_spec/specs/tech/STACK.md

@@ -22,6 +22,7 @@ The application follows a **Tool-Use (Function Calling)** architecture:
     *   Validates the request against the **Safety Policy**.
     *   Executes the native code (File I/O, Shell Process, Search).
     *   Returns the output (stdout/stderr/file content) to the LLM.
+    *   **Event Loop:** The backend emits real-time events (`chat:update`) to the frontend to ensure UI responsiveness during long-running Agent tasks.
 
 ## LLM Provider Abstraction
 To support both Remote and Local models, the system implements a `ModelProvider` abstraction layer.