feat: 优化部分问题，完善选区功能

src/component/Canvas/CanvasEditor/commands/LayerCommands.js

@@ -34,13 +34,21 @@ export class AddLayerCommand extends Command {
     this.insertIndex = options.insertIndex;
     this.oldActiveLayerId = null;
     this.beforeLayers = [...this.layers.value]; // 备份原图层列表
+
+    this.options = options.options || {};
   }
 
   execute() {
     // 保存当前活动图层ID
     this.oldActiveLayerId = this.activeLayerId.value;
 
-    // 执行添加图层操作
+    // 执行添加顶级图层操作
+    if (this.options?.insertTop) {
+      this.layers.value.splice(0, 0, this.newLayer);
+      this.activeLayerId.value = this.newLayer.id;
+      return this.newLayer.id;
+    }
+
     // 智能插入图层到合适位置
     this._insertLayerAtCorrectPosition(this.newLayer);
     // if (this.insertIndex !== undefined && this.insertIndex !== null) {