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.

uv.lock

@@ -117,7 +117,7 @@ name = "blendjob"
 version = "0.1.17"
 source = { path = "src/anyimage/wheels/blendjob-0.1.17-py3-none-any.whl" }
 wheels = [
-    { filename = "blendjob-0.1.17-py3-none-any.whl", hash = "sha256:9173320611ae77ce8852c6f9e96ddcec1b455ac1e2c0d1f886041e5a33e0cc86" },
+    { filename = "blendjob-0.1.17-py3-none-any.whl", hash = "sha256:a300ff10972953e1e930072edf33eed5e0f9342c83b30311341c7a6581c98e95" },
 ]
 
 [package.metadata]