Fix critical bugs and improve laptop compatibility

Major fixes:
- Fix keybinding closure bug causing all zones to map to zone 9
- Change keybindings from Super+Numpad to Super+Ctrl+1-9 for laptop compatibility
- Fix shift-drag detection by implementing continuous modifier polling during window drag
- Fix window object reference by using global.display.focus_window
- Fix window API compatibility (use property checks instead of get_maximized())
- Correct grab-op-begin/end signal handler parameters

Technical improvements:
- Add modifier polling (50ms interval) during window drag to detect Shift key press/release
- Use Mainloop.idle_add to defer window resize operations
- Remove debug logging for production use
- Improve error handling and cleanup in destroy() method

The extension now fully supports:
- Shift-drag window snapping with visual zone overlay
- Keyboard shortcuts for direct zone snapping (Super+Ctrl+1-9)
- Zone overlay toggle (Super+Z)
- Layout cycling (Super+Shift+Z)
- Graphical zone editor (Super+Shift+E)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

README.md

@@ -31,7 +31,7 @@ A window tiling manager extension for Linux Mint's Cinnamon Desktop, inspired by
 - **Super + Z**: Toggle zone overlay (show/hide zones)
 - **Super + Shift + Z**: Cycle through different layouts
 - **Super + Shift + E**: Open graphical zone editor
-- **Super + Numpad 1-9**: Snap focused window to zone 1-9
+- **Super + Ctrl + 1-9**: Snap focused window to zone 1-9
 
 ### Mouse Usage