- Create API endpoint to list directories under /mnt with navigation support
- Detect and indicate already added libraries to prevent duplicates
- Add "Browse" button to library path input for opening modal folder selector
- Implement modal UI with directory navigation, current path display, and selection buttons
- Integrate modal selection with existing library adding workflow
- Show visual feedback by disabling selection of existing libraries
- Update documentation and feature status to include the new IntelliSense feature
- Add test scripts covering IntelliSense navigation and library conflict detection
