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/tools/nodes/test_image_depth_panorama.py

@@ -36,6 +36,7 @@ def panorama(depth=3, alpha=1, subdivide=3, reference=3):
 
     for name, value in (("Depth Image", image), ("Subdivide", subdivide), ("Reference Distance", reference)):
         set_value(name, value)
+    set_value("Boundary Smooth", 0)
     return obj, set_value
 
 
@@ -209,6 +210,7 @@ def test_continuous_spherical_slope_does_not_split_at_seam_or_poles():
     obj, set_value = panorama(depth)
     original = evaluated(obj)
     set_value("Split Threshold", 1)
+    set_value("Boundary Smooth", 12)
     points, faces, uv = evaluated(obj)
     np.testing.assert_allclose(points, original[0], atol=1e-6)
     assert faces == original[1]