Implement a responsive mobile navigation menu for the documentation site,
activated at the 768px breakpoint. Includes a hamburger toggle button in
the header, slide-out menu drawer with overlay, and keyboard/click-to-close
functionality.
- Add mobile menu toggle button with animated icon swap
- Create slide-out menu drawer with documentation navigation
- Add semi-transparent overlay that closes menu on click
- Implement keyboard (Escape) and link-click menu close handlers
- Auto-close menu on viewport resize to desktop sizes
- Add mobile-specific styling for nav items and table of contents
- Load mobile-menu.js script for interaction handling
- Adjust z-index layering for menu drawer (200) and overlay (199)