Add custom shape mask menu with expansion and feathering

Introduces a CustomShapeMenu UI component for managing custom output area shape masks, including options for auto-applying the mask, expansion/contraction, and feathering. Updates Canvas and MaskTool to support these new mask operations, and ensures the menu is shown or hidden based on shape presence. Adds distance transform-based algorithms for accurate mask expansion and feathering.

src/CanvasInteractions.ts

@@ -101,6 +101,7 @@ export class CanvasInteractions {
         const worldCoords = this.canvas.getMouseWorldCoordinates(e);
         const viewCoords = this.canvas.getMouseViewCoordinates(e);
 
+
         if (this.interaction.mode === 'drawingMask') {
             this.canvas.maskTool.handleMouseDown(worldCoords, viewCoords);
             this.canvas.render();
@@ -987,4 +988,5 @@ export class CanvasInteractions {
 
         await this.canvas.canvasLayers.clipboardManager.handlePaste('mouse', preference);
     }
+
 }