Add cutout shell and volume node assets for depth volume processing

- Implemented `cutout_shell.py` to build front normals and shell positions for balloon geometry.
- Created `cutout_volume.py` to establish smooth center fields and manage balloon surface attributes.
- Introduced `pisa_sr_export.py` for exporting PiSA-SR components with dependencies and asset finalization.

tools/node_assets/build.py

@@ -12,10 +12,9 @@ sys.path.insert(
     str(next((PROJECT_ROOT / "src" / "anyimage" / "wheels").glob("blendjob-*.whl"))),
 )
 
-from build_cutout import (
+from build_cutout_modifiers import (
     CUTOUT_NODE_GROUP_NAMES,
-    build_cutout_modifier_group,
-    build_node_group,
+    build_cutout_group,
 )
 from build_depth_plane import build_depth_plane_group
 from build_material_layers import build_material_layer_group
@@ -38,11 +37,8 @@ def main():
     build_material_layer_group()
     build_material_layer_group(depth_plane=True)
     build_shadeless_group()
-    shape_groups = {
-        shape: build_node_group(shape)
-        for shape in CUTOUT_NODE_GROUP_NAMES
-    }
-    build_cutout_modifier_group(shape_groups)
+    for shape in CUTOUT_NODE_GROUP_NAMES:
+        build_cutout_group(shape)
     OUTPUT_PATH.parent.mkdir(parents=True, exist_ok=True)
     bpy.ops.wm.save_as_mainfile(filepath=str(OUTPUT_PATH), check_existing=False)