feat: 优化测量功能架构与引擎组件

- 重构测量激活逻辑，在 Engine 组件中添加统一的 activateMeasure(mode) 方法
- 简化 MeasureDialogManager，移除冗余的 handleMeasureTypeChange 方法
- 添加 EngineManager.activateMeasure 转发方法
- 修复 loadModel 错误，正确调用 Engine 组件方法
- 为 Engine 组件设置固定背景渐变色
- MeasurePanel 初始化时触发 onModeChange 回调
- 添加 MeasureMode 共享类型定义

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.json

@@ -19,8 +19,10 @@
     "dev": "vite",
     "build": "tsc && vite build",
     "copy:demo": "mkdir -p demo/lib && cp dist/bim-engine-sdk.es.js dist/bim-engine-sdk.umd.js dist/bim-engine-sdk.umd.js.map demo/lib/",
+    "copy:demo-draco": "mkdir -p demo/static/js/draco && cp src/engine_base/draco/*.js src/engine_base/draco/*.wasm demo/static/js/draco/",
+    "copy:demo-all": "npm run copy:demo && npm run copy:demo-draco",
     "copy:demo-vue": "mkdir -p demo-vue/public/lib && cp dist/bim-engine-sdk.es.js dist/bim-engine-sdk.umd.js dist/bim-engine-sdk.umd.js.map demo-vue/public/lib/",
-    "dev:demo": "npm run build && npm run copy:demo && cd demo && npm run dev",
+    "dev:demo": "npm run build && npm run copy:demo-all && cd demo && npm run dev",
     "dev:demo-vue": "npm run build && npm run copy:demo-vue && cd demo-vue && npm run dev",
     "dev:all": "npm run dev:demo & npm run dev:demo-vue"
   },
@@ -38,5 +40,8 @@
     "vite": "^7.2.6",
     "vite-plugin-css-injected-by-js": "^3.5.2",
     "vite-plugin-dts": "^4.5.4"
+  },
+  "dependencies": {
+    "three": "^0.182.0"
   }
 }