refactor: slim down EngineManager from 861 to 290 lines by removing passthrough proxy pattern

- EngineManager now only exposes public SDK API (initialize, loadModel, pause/resumeRendering, getEngineComponent, destroy)
- Internal managers access Engine component directly via this.engineComponent getter on BaseManager
- Non-manager components use registry.engine3d.getEngineComponent() for direct Engine access
- Replaced getEngine() with onRawEvent()/offRawEvent() for raw engine event access
- Migrated 62 call sites across 13 files (9 managers, 1 panel, 3 toolbar buttons)
- Updated all architecture docs, API docs, and README to reflect new patterns

src/managers/section-axis-dialog-manager.ts

@@ -64,9 +64,9 @@ export class SectionAxisDialogManager extends BaseDialogManager {
             onHideToggle: (isHidden) => {
                 console.log('[SectionAxisDialogManager] 隐藏切换：', isHidden);
                 if (isHidden) {
-                    this.registry.engine3d?.hideSection();
+                    this.engineComponent?.hideSection();
                 } else {
-                    this.registry.engine3d?.recoverSection();
+                    this.engineComponent?.recoverSection();
                 }
             },
             onReverse: () => {
@@ -75,7 +75,7 @@ export class SectionAxisDialogManager extends BaseDialogManager {
             },
             onAxisChange: (axis) => {
                 console.log('[SectionAxisDialogManager] 切换轴向：', axis);
-                this.registry.engine3d?.activeSection(axis);
+                this.engineComponent?.activeSection(axis);
             }
         });
         this.panel.init();
@@ -87,13 +87,13 @@ export class SectionAxisDialogManager extends BaseDialogManager {
         this.dialog?.fitHeight(false);
         
         // 检查 Engine 是否已初始化
-        if (!this.registry.engine3d) {
+        if (!this.engineComponent) {
             console.error('[SectionAxisDialogManager] Engine not initialized. Call initEngine() first.');
             return;
         }
         
         // 自动激活默认轴向剖切（X轴）
-        this.registry.engine3d.activeSection('x');
+        this.engineComponent.activeSection('x');
     }
 
     /** 对话框关闭时的回调，取消工具栏按钮激活状态 */
@@ -103,7 +103,7 @@ export class SectionAxisDialogManager extends BaseDialogManager {
 
     /** 销毁前的清理，销毁面板实例 */
     protected onBeforeDestroy(): void {
-        this.registry.engine3d?.deactivateSection();
+        this.engineComponent?.deactivateSection();
         
         if (this.panel) {
             this.panel.destroy();