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_cutout_objects.py

@@ -187,7 +187,11 @@ def test_cutout_presets_load_three_direct_modifier_assets():
         assert inputs["Mode"].default_value == "Balloon"
         assert inputs["Smooth"].default_value == 0
         assert inputs["Smooth Weight"].default_value == 1
-        assert "Edge Smooth" not in inputs
+        if shape == "DEPTH_SOLID":
+            assert inputs["Boundary Smooth"].default_value == 5
+            assert inputs["Boundary Smooth"].parent.name == "Options"
+        else:
+            assert "Boundary Smooth" not in inputs
         assert not any(node.bl_idname == "GeometryNodeRepeatInput" and node.inputs["Iterations"].default_value == 8 for node in group.nodes)
     assert next(item for item in groups["DEPTH_BALLOON"].interface.items_tree if item.name == "Double Sided").default_value
 
@@ -424,17 +428,17 @@ def test_depth_surface_keeps_continuous_points_across_zero_validity_edge():
     assert np.ptp(positions[:, 2]) < 1e-4
 
 
-def test_depth_surface_split_removes_isolated_triangle_without_loose_geometry():
+def test_depth_surface_removes_boundary_ears_without_loose_geometry():
     bpy.ops.wm.read_factory_settings(use_empty=True)
     obj, modifier = _depth_surface_step_object()
     split_id = object_data.modifier_input_identifier(modifier.node_group, "Split Threshold")
-    # The raised corner becomes an isolated triangle after separation.
-    for value, expected in ((0., (9, 8)), (.5, (8, 7)), (1., (8, 7))):
+    # Both outer ears have three boundary vertices, including the raised corner.
+    for value in (0., .5, 1.):
         object_data.set_modifier_input(modifier, split_id, value)
         obj.update_tag(refresh={"DATA"})
         bpy.context.view_layer.update()
         vertices, faces, loose_edges, loose_points = _evaluated_topology(obj)
-        assert (vertices, faces) == expected
+        assert (vertices, faces) == (7, 6)
         assert not loose_edges and not loose_points