feat: Implement weight cutout boundary smoothing for image depth cutout

- Added a new proposal for boundary smoothing in the weight cutout process, differentiating between Split edges and Outline smoothing requirements.
- Introduced a new capability `cutout-boundary-smoothing` to control smoothing strength and default values.
- Updated specifications to define the behavior of boundary-specific smoothing strength and default settings.
- Created tasks to verify the implementation of boundary behavior and asset updates.
- Developed comprehensive tests for depth symmetry and normal scaling to ensure expected behavior and performance.
- Introduced new attributes for normal mapping to facilitate persistent face attributes sharing between depth symmetry and image materials.
- Built a new node group for O Image Depth Symmetry, integrating the new smoothing capabilities and ensuring compatibility with existing workflows.

tests/support/nodes.py

@@ -1,11 +1,11 @@
 """Shared assertions and asset selection for node tests."""
 from tools.nodes.groups.image_cutout import build_image_cutout_group
 from tools.nodes.groups.image_depth_cutout import build_image_depth_cutout_group
-from tools.nodes.groups.image_depth_balloon import build_image_depth_balloon_group
+from tools.nodes.groups.image_depth_symmetry import build_image_depth_symmetry_group
 
 CUTOUT_BUILDERS = {
     "FLAT": build_image_cutout_group,
     "SOLID": build_image_cutout_group,
     "DEPTH_SOLID": build_image_depth_cutout_group,
-    "DEPTH_BALLOON": build_image_depth_balloon_group,
+    "DEPTH_SYMMETRY": build_image_depth_symmetry_group,
 }