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.

tests/test_server_jobs.py

@@ -1060,7 +1060,7 @@ class ServerJobsTest(unittest.TestCase):
 
             with Image.open(context.directory / "upscale.0001.png") as result:
                 self.assertEqual(result.mode, "RGBA")
-                self.assertEqual(result.size, (20, 12))
+                self.assertEqual(result.size, (10, 6))
                 alpha = np.asarray(result.getchannel("A"))
                 expected_alpha = np.asarray(
                     Image.fromarray(pixels[:, :, 3], mode="L").resize(