feat: initial implementation of mousefree

Keyboard-driven mouse navigation overlay for Wayland using
wlr-layer-shell and wlr-virtual-pointer. Two-key grid selection,
click/double-click/right-click/drag, three-tier cursor nudge
(hjkl/HJKL/Ctrl+hjkl), and scroll passthrough.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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+*.swp
+*.swo
+.DS_Store
+Thumbs.db