Add tests and implement boundary smoothing and cutout functionality

- Introduced tests for boundary smoothing in `test_boundary_smoothing.py`, verifying that smoothing reduces stair-step artifacts while preserving boundary integrity.
- Added tests for cutout boundary behavior in `test_cutout_boundary.py`, ensuring proper handling of boundary triangles and normal blending.
- Created `test_temporary_attributes.py` to check the cleanup of temporary attributes across depth modifier branches, ensuring no warnings are raised.
- Implemented point culling functionality in `test_validity.py`, confirming that invalid points are removed without affecting adjacent geometry.
- Developed boundary smoothing logic in `boundary_smoothing.py`, allowing for depth smoothing while maintaining edge integrity.
- Added cutout boundary management in `cutout_boundary.py`, including functions for removing boundary triangles and tapering thickness profiles.
- Implemented validity checks in `validity.py` to ensure proper deletion of invalid vertices and associated wire edges.

tests/anyimage/operators/test_plane_objects.py

@@ -73,7 +73,8 @@ def test_clipboard_plane_uses_the_mesh_material_slot():
 
 def test_converted_planes_center_the_origin_without_moving_world_corners():
     bpy.ops.wm.read_factory_settings(use_empty=True)
-    build_image_depth_plane_group(build_image_plane_group())
+    saved = build_image_depth_plane_group(build_image_plane_group())
+    saved["anyimage_asset_revision"] = 11
 
     def create_source(name):
         image = bpy.data.images.new(name, width=200, height=100)
@@ -149,6 +150,9 @@ def test_converted_planes_center_the_origin_without_moving_world_corners():
     assert_centered(depth_plane, depth_bounds, depth_matrix)
     assert depth_plane["anyimage_mesh_shape"] == "DEPTH_PLANE"
     depth_modifier = depth_plane.modifiers[0]
+    assert depth_modifier.node_group != saved
+    assert depth_modifier.node_group["anyimage_asset_revision"] == 14
+    assert saved in bpy.data.node_groups.values() and saved["anyimage_asset_revision"] == 11
     uniform_scale = depth_modifier[
         object_data.modifier_input_identifier(
             depth_modifier.node_group,