Optimize Cutout Geometry Nodes

- Refactor Depth Cutout to reuse the projected outline field, reducing redundant boundary calculations and improving performance.
- Derive the center field from shared low-frequency fields, eliminating an unnecessary blur operation.
- Implement triangle-only strip cleanup for Depth Cutout, as the input is confirmed to be triangulated.
- Short-circuit zero-thickness branches in both Cutout and Depth Cutout to avoid unnecessary geometry generation.
- Standardize internal attribute naming with a new `_o_` prefix and implement wildcard cleanup for temporary attributes.
- Update relevant tests to ensure functionality remains consistent and validate changes against existing behavior.

tests/tools/nodes/test_inventory.py

@@ -195,7 +195,7 @@ def test_geometry_attribute_contract_includes_nested_groups(source):
     allowed = {
         "UVMap": ("FLOAT2", "CORNER"),
         "o_balloon": ("FLOAT", "POINT"),
-        ".o_anyimage_depth_cut": ("BOOLEAN", "CORNER"),
+        "_o_anyimage_depth_cut": ("BOOLEAN", "CORNER"),
         "o_depth_rotation": ("FLOAT_VECTOR", "FACE"),
         "o_depth_face": ("FLOAT", "FACE"),
         "o_depth_axis": ("FLOAT", "FACE"),