feat: Add WebGPU cube example to GitHub Pages

Update GitHub Pages deployment workflow to include the WebGPU rotating cube example:

**Build Steps:**
- Copy wasm_exec.js to webgpu-cube directory
- Build webgpu-cube WASM binary
- Copy built files to _site/webgpu-cube/ for deployment

**Landing Page Updates:**
- Add WebGPU Rotating Cube to examples list
- Include description highlighting 3D graphics, scene graphs, and PBR materials
- Add browser compatibility notice for WebGPU requirements (Chrome 113+, Edge 113+)

The WebGPU cube will be live at `/webgpu-cube/` when deployed to GitHub Pages,
showcasing Guix's ability to handle advanced graphics APIs through WASM.

Author: claude

.github/workflows/pages.yml

@@ -43,13 +43,16 @@ jobs:
           if [ -f "$GOROOT/lib/wasm/wasm_exec.js" ]; then
             cp "$GOROOT/lib/wasm/wasm_exec.js" examples/counter/
             cp "$GOROOT/lib/wasm/wasm_exec.js" examples/calculator/
+            cp "$GOROOT/lib/wasm/wasm_exec.js" examples/webgpu-cube/
           elif [ -f "$GOROOT/misc/wasm/wasm_exec.js" ]; then
             cp "$GOROOT/misc/wasm/wasm_exec.js" examples/counter/
             cp "$GOROOT/misc/wasm/wasm_exec.js" examples/calculator/
+            cp "$GOROOT/misc/wasm/wasm_exec.js" examples/webgpu-cube/
           else
             echo "wasm_exec.js not found in GOROOT, downloading from GitHub"
             curl -o examples/counter/wasm_exec.js https://raw.githubusercontent.com/golang/go/go1.25.0/lib/wasm/wasm_exec.js
             curl -o examples/calculator/wasm_exec.js https://raw.githubusercontent.com/golang/go/go1.25.0/lib/wasm/wasm_exec.js
+            curl -o examples/webgpu-cube/wasm_exec.js https://raw.githubusercontent.com/golang/go/go1.25.0/lib/wasm/wasm_exec.js
           fi
 
       - name: Build counter WASM
@@ -60,17 +63,25 @@ jobs:
         working-directory: examples/calculator
         run: GOOS=js GOARCH=wasm go build -o main.wasm .
 
+      - name: Build WebGPU cube WASM
+        working-directory: examples/webgpu-cube
+        run: GOOS=js GOARCH=wasm go build -o main.wasm .
+
       - name: Create Pages structure
         run: |
           mkdir -p _site
           mkdir -p _site/counter
           mkdir -p _site/calculator
+          mkdir -p _site/webgpu-cube
           cp examples/counter/index.html _site/counter/
           cp examples/counter/main.wasm _site/counter/
           cp examples/counter/wasm_exec.js _site/counter/
           cp examples/calculator/index.html _site/calculator/
           cp examples/calculator/main.wasm _site/calculator/
           cp examples/calculator/wasm_exec.js _site/calculator/
+          cp examples/webgpu-cube/index.html _site/webgpu-cube/
+          cp examples/webgpu-cube/main.wasm _site/webgpu-cube/
+          cp examples/webgpu-cube/wasm_exec.js _site/webgpu-cube/
 
           # Create index page with links to examples
           cat > _site/index.html << 'EOF'
@@ -153,8 +164,22 @@ jobs:
                               <strong>Calculator</strong> - Interactive calculator with state management and event handlers
                           </a>
                       </li>
+                      <li>
+                          <a href="./webgpu-cube/">
+                              <strong>WebGPU Rotating Cube</strong> - 3D graphics with WebGPU, scene graphs, and PBR materials
+                          </a>
+                      </li>
                   </ul>
 
+                  <div class="info">
+                      <h3>Browser Compatibility</h3>
+                      <p>
+                          <strong>Note:</strong> The WebGPU Cube example requires a browser with WebGPU support
+                          (Chrome 113+, Edge 113+, or other WebGPU-enabled browsers). The Counter and Calculator
+                          examples work in all modern browsers.
+                      </p>
+                  </div>
+
                   <div class="info">
                       <h3>Learn More</h3>
                       <p>