Refactor MaterialX demo: rename to mtlx-debug and create simple demo

- Rename materialx.js/html to mtlx-debug.js/html for advanced debug features
- Create new simple materialx.js/html with clean Three.js + TinyUSDZ demo
- New demo features: drag-and-drop USD loading, material parameter UI,
  texture preview, material type switching (OpenPBR/UsdPreviewSurface),
  HDR environment presets, tone mapping controls
- Update README.md with demo pages documentation
- Update MATERIALX-DEMO-README.md with both demo URLs

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

web/js/MATERIALX-DEMO-README.md

@@ -97,7 +97,8 @@ A comprehensive web application for loading, editing, importing, and exporting M
    ```
 
 3. **Open in Browser**:
-   Navigate to `http://localhost:8000/js/materialx.html`
+   - Simple demo: `http://localhost:8000/js/materialx.html`
+   - Advanced debug demo: `http://localhost:8000/js/mtlx-debug.html`
 
 ## Usage
 

web/js/README.md

@@ -162,6 +162,30 @@ const openPBR = new TinyUSDZOpenPBR({
 const threeMaterial = openPBR.toMeshPhysicalMaterial();
 ```
 
+## Demo Pages
+
+The following demo pages are available:
+
+| Demo | File | Description |
+|------|------|-------------|
+| **MaterialX Demo** | `materialx.html` | Simple MaterialX/OpenPBR viewer with drag-and-drop USD loading, material parameter UI, and preset environment lighting |
+| **MaterialX Debug Demo** | `mtlx-debug.html` | Advanced debugging demo with AOV visualization, node graph viewer, texture inspector, and comprehensive PBR debugging tools |
+| **Animation Demo** | `animation.html` | USD animation playback demo |
+| **Skinning Demo** | `skining-anim.html` | Skeletal animation and skinning demo |
+| **UsdLux Demo** | `usdlux.html` | USD Lighting demo |
+| **Basic Viewer** | `index.html` | Basic USD viewer with main.js |
+
+### Running Demos
+
+```bash
+# Start development server
+bun run dev
+
+# Open in browser
+# http://localhost:5173/materialx.html      # Simple MaterialX demo
+# http://localhost:5173/mtlx-debug.html     # Advanced debug demo
+```
+
 ## NPM packaging
 
 NPM packaing is not handled in this folder.