feat(node_assets): add image plane geometry nodes and validation scripts

- Implemented `image_plane.py` to build the Image Plane Geometry Nodes group with customizable parameters for geometry, subdivide, and thickness.
- Created `image_plane_validation.py` to validate the functionality of the image plane, ensuring correct geometry generation and material assignment.
- Developed `material_layers.py` to construct shader node groups for image materials, including depth and normal handling.
- Authored `plane_layouts.py` to define node arrangements for image geometry assets.
- Introduced `shadeless.py` to create a shadeless shader node group that displays color without scene lighting while preserving shadows and reflections.

docs/internals/operators/clipboard-image.md

@@ -38,4 +38,4 @@ flowchart TD
 
 落点仍在 `actions.py` 中完成：3D View 创建 Reference 或 Plane，Node Editor 创建与当前节点树匹配的 Image 节点，绘制模式把 Image 配置为当前画笔的 Texture。鼠标位置和视图位置也在这里换算。
 
-Plane 路径调用 `convert_to_plane/mesh_plane.py` 创建中心原点基础网格，并从节点资产加载 `O Mesh Plane`。`actions.py` 创建图像材质并放入 Mesh 第 `0` 个材质槽，节点组只生成几何。
+Plane 路径调用 `convert_to_plane/image_plane.py` 创建中心原点基础网格，并从节点资产加载 `O Image Plane`。`actions.py` 创建图像材质并放入 Mesh 第 `0` 个材质槽，节点组只生成几何。