Refactor and enhance geometry node groups for depth plane and material layers

- Updated the depth plane node group to load from an asset and simplified the interface.
- Created a new build script for depth plane geometry nodes.
- Introduced material layer groups for image and depth materials with appropriate sockets.
- Added functionality to connect balloon normal scale to the image material.
- Enhanced tests to validate the new node groups and their connections.
- Ensured that production code does not create node groups directly.

docs/guides/depth-plane.md

@@ -18,7 +18,7 @@ Depth Plane 将一张静态图片转换为带深度位移的网格，适合快
 
 ## 调整结果
 
-生成对象使用运行时创建的 `O Image Depth Plane` Geometry Nodes 修改器：
+生成对象使用扩展资产中的 `O Image Depth Plane` Geometry Nodes 修改器：
 
 - **Subdivide**：控制基础平面细分级别；
 - **Thickness**：增加背面和侧壁，`0` 输出单面；