feat: enhance follow-up feature handling and improve async processing

- Implemented asynchronous follow-up work in AutoModeService to allow immediate API response, enabling smoother user experience.
- Updated BoardView to handle follow-up prompts more efficiently, including state management and success notifications.
- Adjusted mock AutoMode API to simulate background processing for follow-up tasks, aligning with real implementation behavior.

These changes streamline the workflow for sending follow-up prompts and improve the responsiveness of the UI.

app/src/lib/electron.ts

@@ -585,9 +585,11 @@ function createMockAutoModeAPI(): AutoModeAPI {
       mockRunningFeatures.add(featureId);
 
       // Simulate follow-up work (similar to run but with additional context)
+      // Note: We don't await this - it runs in the background like the real implementation
       simulateAutoModeLoop(projectPath, featureId);
 
-      return { success: true, passes: true };
+      // Return immediately so the modal can close (matches real implementation)
+      return { success: true };
     },
 
     commitFeature: async (projectPath: string, featureId: string) => {