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.

src/anyimage/operators/cutout_tool/__init__.py

@@ -0,0 +1,12 @@
+"""Cutout selection, shape conversion, and geometry algorithms."""
+
+from .selection_tool import ActivateCutoutTool, CutoutTool, SelectCutoutRegion
+from .shape_conversion import ConvertCutoutShape, GenerateCutoutShape
+
+__all__ = (
+    "ActivateCutoutTool",
+    "ConvertCutoutShape",
+    "CutoutTool",
+    "GenerateCutoutShape",
+    "SelectCutoutRegion",
+)