feat: Add computer use tools for remote and local GUI automation

[edenreich]

Adds computer use capabilities including screenshot capture, mouse movement, mouse clicks, and keyboard typing. Includes a complete Docker-based example with Ubuntu GUI desktop, X11/Wayland support, and live screenshot streaming to web UI. Closes #358.

Key features:

• Screenshot tool with streaming support
• Mouse control (move and click)
• Keyboard input (text and key combos)
• Rate limiting and approval system
• Complete Docker example with web UI integration

Technical details:

• Supports both X11 and Wayland display servers
• Screenshot streaming via WebSocket for live desktop viewing
• Circular buffer for efficient screenshot storage
• Rate limiting to prevent abuse
• User approval system for sensitive operations
• Docker example with headless Ubuntu desktop setup

[edenreich]

TODOs

• Check whether it's a good idea to replace the switch from terminal to active window and back with a GUI window that is always on top - similar to how vercept AI is doing it and only show this when computer use is enabled and it's not a remote session over pty - basically only for local computer use it's necessary because the window is constantly changing focus
• I should probably also have a visual indicator that the computer is currently watched when computer_use.screenshot.streaming is enabled