Prevent LayerForge from intercepting Ctrl+C, Ctrl+V, and other keyboard
shortcuts when the canvas is not focused. This was causing unwanted
popups and interfering with other nodes in ComfyUI.
Changes:
- Remove document.body focus check from handlePasteEvent
- Add focus validation to handleKeyDown before processing shortcuts
- Modifier keys (Ctrl, Shift, Alt, Meta) are still tracked globally
- All other shortcuts only trigger when canvas is focused
Fixes issue where paste events were captured globally regardless of focus.