Prevent browser context menu on custom right-click menus

Always prevent the default browser context menu and stop event propagation on right-click interactions and custom menus. This ensures that only the application's custom context menus are shown and avoids interference from the browser's native context menu.

src/CanvasLayers.ts

@@ -739,6 +739,12 @@ export class CanvasLayers {
             content.appendChild(container);
         });
 
+        // Add contextmenu event listener to the menu itself to prevent browser context menu
+        menu.addEventListener('contextmenu', (e: MouseEvent) => {
+            e.preventDefault();
+            e.stopPropagation();
+        });
+
         const container = this.canvas.canvas.parentElement || document.body;
         container.appendChild(menu);