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/node_assets/depth_plane_camera.py

@@ -0,0 +1,44 @@
+"""Build the camera-projected branch of the complete-image depth plane."""
+
+from node_graph import group_input as _group_input
+from depth_surface import project_depth_surface, thicken_depth_surface, remove_surface_attributes
+
+
+def build_camera_plane(group, image_plane_group):
+    nodes, links = group.nodes, group.links
+    controls = _group_input(nodes, (-300, 0), {"Geometry", "Subdivide"})
+    plane = nodes.new("GeometryNodeGroup")
+    plane.node_tree = image_plane_group
+    plane.inputs["Thickness"].default_value = 0
+    links.new(controls.outputs["Geometry"], plane.inputs["Geometry"])
+    links.new(controls.outputs["Subdivide"], plane.inputs["Subdivide"])
+    texture_input = _group_input(nodes, (-300, 700), {"Depth Image", "Uniform Scale"})
+    uv = nodes.new("GeometryNodeInputNamedAttribute")
+    uv.data_type = "FLOAT_VECTOR"
+    uv.inputs["Name"].default_value = "UVMap"
+    texture = nodes.new("GeometryNodeImageTexture")
+    texture.interpolation, texture.extension = "Linear", "EXTEND"
+    links.new(uv.outputs["Attribute"], texture.inputs["Vector"])
+    links.new(texture_input.outputs["Depth Image"], texture.inputs["Image"])
+    depth_input = _group_input(nodes, (500, 1000), {"Reference Depth", "Depth Scale"})
+    surface = project_depth_surface(
+        group, plane.outputs["Geometry"], texture.outputs["Color"],
+        texture_input.outputs["Uniform Scale"], depth_input.outputs["Reference Depth"],
+        depth_input.outputs["Depth Scale"],
+    )
+    shell_input = _group_input(nodes, (2000, 500), {"Camera Thickness", "Normal Smooth"})
+    shell = thicken_depth_surface(
+        group, surface, shell_input.outputs["Camera Thickness"],
+        normal_smooth=shell_input.outputs["Normal Smooth"],
+    )
+    positive = nodes.new("ShaderNodeMath")
+    positive.operation = "GREATER_THAN"
+    links.new(shell_input.outputs["Camera Thickness"], positive.inputs[0])
+    positive.inputs[1].default_value = 0
+    choose = nodes.new("GeometryNodeSwitch")
+    choose.input_type = "GEOMETRY"
+    links.new(positive.outputs[0], choose.inputs["Switch"])
+    links.new(surface, choose.inputs["False"])
+    links.new(shell, choose.inputs["True"])
+    clean = remove_surface_attributes(group, choose.outputs["Output"])
+    return clean