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.

src/anyimage/properties.py

@@ -251,8 +251,8 @@ def cutout_generate_normal_property():
     return bpy.props.BoolProperty(
         name="Normal Map",
         description=(
-            "Generate a MoGe-2 normal texture; Depth Surface uses Object Space "
-            "and other shapes use Tangent Space"
+            "Generate a normal map for Flat and Solid; "
+            "Depth Solid and Depth Balloon always generate normal maps"
         ),
         default=False,
     )