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.

js/MaskTool.js

@@ -209,9 +209,6 @@ export class MaskTool {
         maskImage.src = tempCanvas.toDataURL();
         return maskImage;
     }
-    get maskContext() {
-        return this.maskCtx;
-    }
     resize(width, height) {
         this.initPreviewCanvas();
         const oldMask = this.maskCanvas;