Implement AI Host functionality with model caching and job management

- Added ai_host.py to handle AI tasks with FastAPI integration.
- Introduced HostState and ModelCache classes for managing client connections and model loading.
- Implemented job submission and cancellation endpoints in the AI host.
- Enhanced tests for AI host functionality, including client tracking and job cancellation.
- Updated existing tests to accommodate changes in the operator and command structure.
- Refactored runtime commands to use request-based architecture instead of command-line arguments.
- Improved model loading logic to handle CUDA memory management and reuse models efficiently.

tests/test_pack.py

@@ -38,5 +38,6 @@ class PackTest(unittest.TestCase):
         self.assertIn("image_depth.py", names)
         self.assertNotIn("snapform_depth_plane.py", names)
         self.assertIn("worker.py", names)
+        self.assertIn("ai_host.py", names)
         self.assertNotIn("importer.py", names)
         self.assertNotIn("snapform/__init__.py", names)