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_bootstrap_runtime.py

@@ -29,6 +29,7 @@ class BootstrapRuntimeTest(unittest.TestCase):
             args = SimpleNamespace(
                 uv="uv",
                 runtime_dir=str(runtime_dir),
+                models_dir=str(root / "models"),
                 backend="cu128",
                 da3_commit="test-commit",
                 ben2_commit="test-ben2-commit",
@@ -67,13 +68,48 @@ class BootstrapRuntimeTest(unittest.TestCase):
         self.assertTrue(
             any("test-ben2-commit" in str(value) for value in ben2_command)
         )
-        check_command = commands[-1]
+        host_command = next(
+            command
+            for command in commands
+            if f"fastapi=={bootstrap.FASTAPI_VERSION}" in command
+        )
+        self.assertIn(f"uvicorn=={bootstrap.UVICORN_VERSION}", host_command)
+        check_command = next(
+            command
+            for command in commands
+            if any("import torch;" in str(value) for value in command)
+        )
         self.assertTrue(
             any(
                 "from ben2 import BEN_Base" in str(value)
                 for value in check_command
             )
         )
+        self.assertTrue(
+            any("import fastapi, uvicorn" in str(value) for value in check_command)
+        )
+        default_downloads = [
+            command
+            for command in commands
+            if any(
+                repository in command
+                for repository in (
+                    "depth-anything/DA3-SMALL",
+                    "depth-anything/DA3-BASE",
+                    "PramaLLC/BEN2",
+                )
+            )
+        ]
+        self.assertEqual(len(default_downloads), 3)
+        ben2_download = next(
+            command
+            for command in default_downloads
+            if "PramaLLC/BEN2" in command
+        )
+        self.assertEqual(
+            ben2_download[-1],
+            '["config.json", "model.safetensors"]',
+        )
 
 
 if __name__ == "__main__":