feat: add support for dual frontend (JS and React) in the CCW application

- Updated CLI to include `--frontend` option for selecting frontend type (js, react, both).
- Modified serve command to start React frontend when specified.
- Implemented React frontend startup and shutdown logic.
- Enhanced server routing to handle requests for both JS and React frontends.
- Added workspace selector component with i18n support.
- Updated tests to reflect changes in header and A2UI components.
- Introduced new Radix UI components for improved UI consistency.
- Refactored A2UIButton and A2UIDateTimeInput components for better code clarity.
- Created migration plan for gradual transition from JS to React frontend.

ccw/frontend/src/components/layout/Header.test.tsx

@@ -162,12 +162,20 @@ describe('Header Component - i18n Tests', () => {
       expect(brandLink).toBeInTheDocument();
     });
 
-    it('should display project path when provided', () => {
+    it('should render workspace selector when project path is provided', () => {
       render(<Header projectPath="/test/path" />);
 
-      // Should show the path indicator
-      const pathDisplay = screen.getByTitle('/test/path');
-      expect(pathDisplay).toBeInTheDocument();
+      // Should render the workspace selector button with aria-label
+      const workspaceButton = screen.getByRole('button', { name: /workspace selector/i });
+      expect(workspaceButton).toBeInTheDocument();
+    });
+
+    it('should not render workspace selector when project path is empty', () => {
+      render(<Header projectPath="" />);
+
+      // Should NOT render the workspace selector button
+      const workspaceButton = screen.queryByRole('button', { name: /workspace selector/i });
+      expect(workspaceButton).not.toBeInTheDocument();
     });
   });