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.

tests/test_node_asset_launcher.py

@@ -1,7 +1,6 @@
 import importlib.util
 from pathlib import Path
 from unittest.mock import patch
-
 import pytest
 
 
@@ -70,3 +69,24 @@ def test_blender_path_reports_missing_configuration(tmp_path):
     ):
         with pytest.raises(RuntimeError, match="Blender not found"):
             launcher.blender_path()
+
+
+def test_launcher_runs_asset_build_and_validations_before_tests(monkeypatch, tmp_path):
+    launcher = load_launcher()
+    executable = tmp_path / "blender"
+    executable.touch()
+    calls = []
+    monkeypatch.setattr(launcher, "blender_path", lambda _: executable)
+    monkeypatch.setattr(launcher, "run", calls.append)
+    monkeypatch.setattr("sys.argv", ["build_node"])
+
+    launcher.main()
+
+    scripts = [Path(command[-1]) for command in calls[:-1]]
+    assert [path.name for path in scripts] == [
+        "asset_library.py", "asset_validation.py",
+        "image_plane_validation.py", "cutout_validation.py",
+    ]
+    assert all(path.is_file() for path in scripts)
+    assert all(command[1:4] == ("--factory-startup", "--background", "--python") for command in calls[:-1])
+    assert calls[-1][1:] == ("-m", "pytest")