✨ Add selection box extension

frontend/src/i18n/locales/en-US.ts

@@ -193,6 +193,10 @@ export default {
       description: 'Highlight selected text content (Ctrl+Shift+H to toggle highlight)',
       backgroundColor: 'Background Color',
       opacity: 'Opacity'
+    },
+    checkbox: {
+      name: 'Checkbox',
+      description: 'Render [x] and [ ] as interactive checkboxes'
     }
   }
 }; 

frontend/src/i18n/locales/zh-CN.ts

@@ -193,6 +193,10 @@ export default {
       description: '高亮选中的文本内容 (Ctrl+Shift+H 切换高亮)',
       backgroundColor: '背景颜色',
       opacity: '透明度'
+    },
+    checkbox: {
+      name: '选择框',
+      description: '将 [x] 和 [ ] 渲染为可交互的选择框'
     }
   }
 };