- Configure hidden title bar with titleBarOverlay matching dark theme
- Remove native menu bar via Menu.setApplicationMenu(null)
- Fix backgroundColor mismatch (#0f172a -> #09090b)
- Add full-width drag region in AppShell for window dragging
- Adjust sidebar and chat headers with top padding for overlay zone
- Add ThinkingDots component with animated dot sequence
- Show activity indicator in chat when agent is processing
- Replace 'Generating...' spinner with inline blinking cursor
- Refine header status badge to subtle pulsing dot
- Add BACKEND_UI_CHANGES.md documenting future sidecar protocol additions
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>