chore(async): move async related code to its directory at top level (#2003)

* chore(async): move async related code to its directory at top level

* chore(style): apply pre-commit to renamed headers

* test(async): fix async imports

* docs(async): update async headers doc

tests/async_inference/test_policy_server.py

@@ -65,8 +65,8 @@ class MockPolicy:
 def policy_server():
     """Fresh `PolicyServer` instance with a stubbed-out policy model."""
     # Import only when the test actually runs (after decorator check)
-    from lerobot.scripts.server.configs import PolicyServerConfig
-    from lerobot.scripts.server.policy_server import PolicyServer
+    from lerobot.async_inference.configs import PolicyServerConfig
+    from lerobot.async_inference.policy_server import PolicyServer
 
     test_config = PolicyServerConfig(host="localhost", port=9999)
     server = PolicyServer(test_config)
@@ -95,7 +95,7 @@ def policy_server():
 def _make_obs(state: torch.Tensor, timestep: int = 0, must_go: bool = False):
     """Create a TimedObservation with a given state vector."""
     # Import only when needed
-    from lerobot.scripts.server.helpers import TimedObservation
+    from lerobot.async_inference.helpers import TimedObservation
 
     return TimedObservation(
         observation={
@@ -191,7 +191,7 @@ def test_obs_sanity_checks(policy_server):
 def test_predict_action_chunk(monkeypatch, policy_server):
     """End-to-end test of `_predict_action_chunk` with a stubbed _get_action_chunk."""
     # Import only when needed
-    from lerobot.scripts.server.policy_server import PolicyServer
+    from lerobot.async_inference.policy_server import PolicyServer
 
     # Force server to act-style policy; patch method to return deterministic tensor
     policy_server.policy_type = "act"