Enhance device management and model handling in SnapForm

- Updated frame extraction logic to allow for single frame extraction.
- Integrated model readiness checks for BEN2 and DA3 models in relevant operators.
- Added directory name attribute to model specifications for better organization.
- Improved device selection logic for production and debug tasks.
- Refactored preferences to expose device settings and ensure they reflect available hardware.
- Enhanced runtime device detection and management, including support for CUDA and MPS.
- Updated tests to cover new device management features and model directory handling.
- Removed deprecated download model tests to streamline codebase.

tests/test_ai_host.py

@@ -109,7 +109,7 @@ class HostTest(unittest.TestCase):
 
         self.assertIs(first, second)
         self.assertEqual(loads, ["model"])
-        self.assertEqual(cache.status()["da3"], "da3_model")
+        self.assertEqual(cache.status()["da3"], "model")
 
     def test_host_tracks_clients_and_rejects_shared_shutdown(self):
         fake_models = SimpleNamespace(