merge: resolve conflicts with master, add inbound attachment materialization

- Delete localagent.py and test_difysvapi_runner.py (replaced by plugins)
- Keep master's tool loader enhancements (byte_offset, encoding params)
- Remove feature branch's artifact reference code (use sandbox paths instead)
- Add _materialize_inbound_attachments in orchestrator for sandbox file staging
- Keep master's test formatting and new tests
- Keep master's frontend refactoring

tests/utils/__init__.py

@@ -1,3 +1,3 @@
 """
 Test utilities package.
-"""
+"""

tests/utils/import_isolation.py

@@ -26,6 +26,7 @@ from unittest.mock import MagicMock
 
 class MockLifecycleControlScope(enum.Enum):
     """Mock enum for breaking circular import in core.entities."""
+
     APPLICATION = 'application'
     PLATFORM = 'platform'
     PLUGIN = 'plugin'