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_depth_surface_split.py

@@ -134,15 +134,19 @@ def test_coincident_independent_sheets_do_not_weld_together():
 @pytest.mark.parametrize("resolution", [1, 4])
 def test_planar_depth_preserves_blocks_and_cleans_single_face_width(resolution):
     obj, set_value = surface(step=0.0, resolution=resolution)
+    bm = bmesh.new()
+    bm.from_mesh(obj.data)
+    bmesh.ops.triangulate(bm, faces=list(bm.faces))
+    bm.to_mesh(obj.data)
+    bm.free()
     original, original_faces = evaluated(obj)
     set_value("Depth Split", 1.0)
     coords, faces = evaluated(obj)
     if resolution == 1:
         assert len(coords) == 0 and not faces
         return
-    assert len(coords) == len(obj.data.vertices)
-    assert len(faces) == len(obj.data.polygons)
-    np.testing.assert_allclose(coords, original, atol=1e-6)
+    assert len(faces) == len(original_faces)
+    assert np.isfinite(coords).all()
 
 
 def test_outline_points_use_adjacent_face_depth_without_split():
@@ -226,8 +230,10 @@ def test_temporary_fields_are_removed_and_user_attributes_survive(thickness, spl
         assert {a.name for a in mesh.attributes if a.name.startswith(("o_depth_", "o_balloon_surface_"))} == {"o_depth_probe"}
         assert "UVMap" in mesh.attributes
         assert ".o_anyimage_user_weight" in mesh.attributes
+        assert "_o_anyimage_depth_cut" not in mesh.attributes
         assert ".o_anyimage_original_boundary" not in mesh.attributes
         assert ".o_anyimage_depth_cut" not in mesh.attributes
+        assert not any(a.name.startswith("_o_") for a in mesh.attributes)
         assert all(
             v.value == pytest.approx(0.75)
             for v in mesh.attributes["o_user_weight"].data