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-lock.json

@@ -8,6 +8,9 @@
       "name": "bim-engine-sdk",
       "version": "1.0.0",
       "license": "ISC",
+      "dependencies": {
+        "three": "^0.182.0"
+      },
       "devDependencies": {
         "@types/node": "^25.0.2",
         "typescript": "^5.9.3",
@@ -1965,6 +1968,12 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/three": {
+      "version": "0.182.0",
+      "resolved": "https://registry.npmmirror.com/three/-/three-0.182.0.tgz",
+      "integrity": "sha512-GbHabT+Irv+ihI1/f5kIIsZ+Ef9Sl5A1Y7imvS5RQjWgtTPfPnZ43JmlYI7NtCRDK9zir20lQpfg8/9Yd02OvQ==",
+      "license": "MIT"
+    },
     "node_modules/tinyglobby": {
       "version": "0.2.15",
       "resolved": "https://registry.npmmirror.com/tinyglobby/-/tinyglobby-0.2.15.tgz",