Add a new `computer` tool that enables agents to control desktop GUIs:
- Take screenshots
- Click, double-click, right-click at coordinates
- Type text, press keys, hotkey combinations
- Scroll in any direction
- Move cursor, drag operations
- Get screen size and cursor position
Integrates with cua-computer-server which can run in:
- Sandbox mode (cua-xfce, cua-ubuntu Docker images)
- Node mode (Linux with supervisor setup)
Includes setup documentation and example screenshot.
