Introduces a new extension API that allows extensions to provide context menu items directly, without monkey-patching. This provides a clean, type-safe way for extensions to add menu items.
**New API methods:**
- `getCanvasMenuItems(canvas)`: Add items to canvas right-click menus
- `getNodeMenuItems(node)`: Add items to node right-click menus
**Implementation:**
- Added TypeScript interfaces in `src/types/comfy.ts`
- Added collection methods in `ComfyApp` class
- Comprehensive test coverage for the new API