Remove Clipspace integration from CanvasView

Eliminates the sendCanvasToClipspace method and related UI/menu options from CanvasView and its TypeScript counterpart, as well as the associated type definition. Also removes the unused maskContext getter from MaskTool. This refactor likely reflects a change in feature requirements or a move away from Impact Pack compatibility.

src/types.ts

@@ -32,7 +32,6 @@ export interface ComfyNode {
     addDOMWidget: (name: string, type: string, element: HTMLElement, options?: any) => any;
     addWidget: (type: string, name: string, value: any, callback?: (value: any) => void, options?: any) => any;
     setDirtyCanvas: (force: boolean, dirty: boolean) => void;
-    sendCanvasToClipspace?: () => Promise<void>;
 }
 
 declare global {