[refactor] Extract keybinding functionality into @comfyorg/keybinding package

Create framework-agnostic keybinding package following domain-driven design patterns.
Move pure business logic to package while keeping Vue integration in workbench layer.

Changes:
- Add @comfyorg/keybinding package with KeyComboImpl and KeybindingImpl classes
- Move core keybindings and reserved key constants to package
- Update workbench layer to import from package with backward compatibility
- Update all imports across codebase to use package exports
- Maintain existing API surface for consumers

tests-ui/tests/store/keybindingStore.test.ts

@@ -1,10 +1,8 @@
+import { KeybindingImpl } from '@comfyorg/keybinding'
 import { createPinia, setActivePinia } from 'pinia'
 import { beforeEach, describe, expect, it } from 'vitest'
 
-import {
-  KeybindingImpl,
-  useKeybindingStore
-} from '@/workbench/keybindings/stores/keybindingStore'
+import { useKeybindingStore } from '@/workbench/keybindings/stores/keybindingStore'
 
 describe('useKeybindingStore', () => {
   beforeEach(() => {