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.

tools/build_node.py

@@ -8,10 +8,10 @@ from pathlib import Path
 
 PROJECT_ROOT = Path(__file__).resolve().parents[1]
 BLENDER_SCRIPTS = (
-    "build.py",
-    "validate.py",
-    "validate_mesh_plane.py",
-    "validate_cutout.py",
+    "asset_library.py",
+    "asset_validation.py",
+    "image_plane_validation.py",
+    "cutout_validation.py",
 )