关闭 3D 预览面板时清掉查看器状态

- src/components/image-editor/model3d-preview/Model3dViewerModal.tsx：layer 变 null（面板关闭）时把 viewerStatus 复位，下一次打开从禁用的「重置视角」开始，不再继承上一轮实例的 ready；只处理关闭不处理换模型，避免 effect 晚于查看器上报而盖掉 loading
- src/components/image-editor/model3d-preview/Model3dViewerModal.test.tsx：新增「关闭后重开不沿用 ready」的回归用例

验证：npx vitest run src/components/image-editor/model3d-preview（18 用例全绿）

src/components/image-editor/model3d-preview/Model3dViewerModal.test.tsx

@@ -195,4 +195,20 @@ describe('Model3dViewerModal', () => {
 
     expect(screen.queryByRole('dialog', { name: '3D模型预览' })).toBeNull();
   });
+
+  it('关闭面板后重开不沿用上一轮的 ready 状态', () => {
+    const layer = createLayer();
+    const { rerender } = renderModal(layer);
+    const resetButton = () =>
+      screen.getByRole('button', { name: '重置视角' }) as HTMLButtonElement;
+
+    expect(resetButton().disabled).toBe(false);
+
+    rerender(<Model3dViewerModal layer={null} onClose={vi.fn()} />);
+    // 重开后的新查看器本轮不上报状态，按钮必须保持禁用，不能继承上一轮的 ready。
+    reportedStatus.status = 'idle';
+    rerender(<Model3dViewerModal layer={layer} onClose={vi.fn()} />);
+
+    expect(resetButton().disabled).toBe(true);
+  });
 });

src/components/image-editor/model3d-preview/Model3dViewerModal.tsx

@@ -5,7 +5,7 @@ import {
   type Model3dViewerStatus,
   type Model3dViewerStatusDetail,
 } from '@genarrative/model3d-viewer';
-import { useRef, useState } from 'react';
+import { useEffect, useRef, useState } from 'react';
 
 import { useResolvedAssetReadUrl } from '../../../hooks/useResolvedAssetReadUrl';
 import { PlatformActionButton } from '../../common/PlatformActionButton';
@@ -111,6 +111,14 @@ export function Model3dViewerModal({
     MODEL3D_VIEWER_FAILURE_FALLBACK_TEXT,
   );
 
+  // 面板关闭（layer 变 null）时清掉状态，让下一次打开从禁用的「重置视角」重新开始。
+  // 只处理关闭、不处理换模型：换模型时查看器会立刻上报，effect 晚一步会把 loading 盖掉。
+  useEffect(() => {
+    if (viewerIdentity === null) {
+      setViewerStatus(null);
+    }
+  }, [viewerIdentity]);
+
   return (
     <UnifiedModal
       open={Boolean(layer)}