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/common/object.py

@@ -3,11 +3,11 @@
 import bpy
 
 
-def modifier_input_identifier(node_group, name):
+def modifier_input_identifier(node_group, name, *, subtype=None):
     for item in node_group.interface.items_tree:
         if item.item_type != "SOCKET" or item.in_out != "INPUT":
             continue
-        if item.name == name:
+        if item.name == name and (subtype is None or getattr(item, "subtype", None) == subtype):
             return item.identifier
     raise RuntimeError(f"Geometry Nodes input is missing: {name}")