feat: Add BEN2 background removal functionality and integrate into SnapForm

- Introduced BEN2 model for background removal in the panel and properties.
- Updated runtime to handle background removal commands and model downloads.
- Implemented background removal logic in worker, including image processing and saving results.
- Enhanced tests to cover new background removal features and ensure proper integration.
- Updated version to 0.9.28 to reflect new features and improvements.

tests/test_models.py

@@ -43,3 +43,14 @@ class ModelTest(unittest.TestCase):
     def test_unknown_model_is_rejected(self):
         with self.assertRaisesRegex(ValueError, "Unknown DA3 model"):
             self.models.get_model("UNKNOWN")
+
+    def test_ben2_download_only_includes_required_hugging_face_files(self):
+        model = self.models.get_downloadable_model("BEN2_BASE")
+
+        self.assertEqual(model.repository, "PramaLLC/BEN2")
+        self.assertEqual(model.license_name, "MIT")
+        self.assertEqual(
+            model.download_patterns,
+            ("config.json", "model.safetensors"),
+        )
+        self.assertNotIn("BEN2_BASE", self.models.MODELS)