Add new node asset scripts for geometry and shader operations

- Implemented `build_mesh_plane.py` to create a geometry node group for mesh planes with customizable parameters.
- Created `build_shadeless.py` for a shader node group that displays color without scene lighting while preserving shadows and reflections.
- Added `validate.py` to validate the integrity of the newly created node groups and their inputs.
- Introduced `validate_cutout.py` to ensure the functionality of cutout node groups and their dependencies.
- Developed `validate_mesh_plane.py` to test the mesh plane creation and its modifier settings.

tests/test_clipboard_image.py

@@ -52,8 +52,11 @@ class ClipboardImageTest(unittest.TestCase):
         cls.addon = ModuleType("anyimage")
         cls.addon.__path__ = [str(PROJECT_ROOT / "src" / "anyimage")]
         sys.modules["anyimage"] = cls.addon
+        operators = ModuleType("anyimage.operators")
+        operators.__path__ = [str(PROJECT_ROOT / "src" / "anyimage" / "operators")]
+        sys.modules["anyimage.operators"] = operators
         cls.addon.clipboard_image = importlib.import_module(
-            "anyimage.clipboard_image"
+            "anyimage.operators.clipboard_image"
         )
         cls.actions = cls.addon.clipboard_image.actions
         cls.clipboard = cls.addon.clipboard_image.clipboard
@@ -318,14 +321,6 @@ class ClipboardImageTest(unittest.TestCase):
             (2 / 3, 1.0),
         )
 
-    def test_plane_creation_delegates_to_mesh_plane_geometry_nodes(self):
-        import inspect
-
-        source = inspect.getsource(self.actions.add_image_plane)
-        self.assertIn("create_mesh_plane_object", source)
-        self.assertNotIn("_plane_grid", source)
-        self.assertNotIn("_block_grid", source)
-
     def test_plane_import_defaults_to_reference_image(self):
         options = (
             self.addon.clipboard_image.PasteClipboardImage