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.

tools/nodes/common/validity.py

@@ -0,0 +1,21 @@
+"""Remove invalid vertices and the wire edges left by point deletion."""
+
+
+def delete_invalid_points(group, geometry, invalid):
+    nodes, links = group.nodes, group.links
+    delete = nodes.new("GeometryNodeDeleteGeometry")
+    delete.domain, delete.mode = "POINT", "ALL"
+    links.new(geometry, delete.inputs["Geometry"])
+    links.new(invalid, delete.inputs["Selection"])
+    neighbors = nodes.new("GeometryNodeInputMeshEdgeNeighbors")
+    wire = nodes.new("FunctionNodeCompare")
+    wire.data_type, wire.operation = "INT", "EQUAL"
+    a = next(socket for socket in wire.inputs if socket.identifier == "A_INT")
+    b = next(socket for socket in wire.inputs if socket.identifier == "B_INT")
+    b.default_value = 0
+    links.new(neighbors.outputs["Face Count"], a)
+    cleanup = nodes.new("GeometryNodeDeleteGeometry")
+    cleanup.domain, cleanup.mode = "EDGE", "ALL"
+    links.new(delete.outputs["Geometry"], cleanup.inputs["Geometry"])
+    links.new(wire.outputs["Result"], cleanup.inputs["Selection"])
+    return cleanup.outputs["Geometry"]