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/common_test_support.py

@@ -0,0 +1,88 @@
+import importlib
+import importlib.util
+import sys
+from pathlib import Path
+from types import ModuleType, SimpleNamespace
+from unittest.mock import patch
+from blender_test_support import mock_bpy_imports
+
+PROJECT_ROOT = Path(__file__).resolve().parents[1]
+
+SOURCE_ROOT = PROJECT_ROOT / "src"
+
+sys.path.insert(0, str(SOURCE_ROOT))
+
+def load_common_modules():
+    fake_bpy = ModuleType("bpy")
+    fake_bpy.props = SimpleNamespace(
+        BoolProperty=lambda **options: options,
+        EnumProperty=lambda **options: options,
+        FloatProperty=lambda **options: options,
+        IntProperty=lambda **options: options,
+        StringProperty=lambda **options: options,
+    )
+    fake_bpy.types = SimpleNamespace(Menu=object, Operator=object)
+    fake_bpy.path = SimpleNamespace(abspath=lambda path: path)
+    fake_bpy.context = SimpleNamespace(scene=None)
+
+    module_paths = (
+        (
+            "anyimage.common.image",
+            PROJECT_ROOT
+            / "src"
+            / "anyimage"
+            / "common"
+            / "image.py",
+        ),
+        (
+            "anyimage.common.node",
+            PROJECT_ROOT
+            / "src"
+            / "anyimage"
+            / "common"
+            / "node.py",
+        ),
+        (
+            "anyimage.common.material",
+            PROJECT_ROOT
+            / "src"
+            / "anyimage"
+            / "common"
+            / "material.py",
+        ),
+        (
+            "anyimage.common.object",
+            PROJECT_ROOT
+            / "src"
+            / "anyimage"
+            / "common"
+            / "object.py",
+        ),
+    )
+    packages = {
+        name: ModuleType(name)
+        for name in (
+            "anyimage",
+            "anyimage.operators",
+            "anyimage.common",
+            "anyimage.operators.convert_to_plane",
+        )
+    }
+    for package in packages.values():
+        package.__path__ = []
+
+    loaded = []
+    preferences = ModuleType("anyimage.preferences")
+    preferences.configured_material_view_adaptation = lambda: True
+    with mock_bpy_imports(fake_bpy), patch.dict(sys.modules, {"anyimage.preferences": preferences, **packages}):
+        for module_name, module_path in module_paths:
+            specification = importlib.util.spec_from_file_location(
+                module_name,
+                module_path,
+            )
+            module = importlib.util.module_from_spec(specification)
+            sys.modules[module_name] = module
+            specification.loader.exec_module(module)
+            loaded.append(module)
+
+    return SimpleNamespace(image=loaded[0], node=loaded[1], material=loaded[2], object=loaded[3])