Add keyboard and mouse input abilities to mdx web

[copilot-developer-agent-robch]

This PR implements interactive features for the mdx web command, enhancing usability by adding keyboard shortcuts and mouse controls. Key features:

• Added InteractiveHelpers class to manage keyboard/mouse interactions
• Navigation shortcuts:
  • j/k: scroll up/down
  • n/p: next/previous page
  • ESC/q: exit interactive mode
• Mouse support:
  • Text selection with click and drag
  • Double click for word selection
  • Triple click for line selection
  • Copy selected text with 'y' key
• Interactive mode improvements:
  • Help overlay (press 'h')
  • Window maximized by default
  • Persistent keyboard event monitoring
  • Non-blocking UI with smooth scrolling

Usage:

mdx web --interactive "your search query"

The PR includes comprehensive help documentation in interactive.txt and integrates smoothly with existing web functionality while maintaining backward compatibility.

Fixes #9.