fix(actor): move namespace filter inside lock in ActorLoader.list_actors

ISSUES CLOSED: #8588

Replace type: ignore suppressions with cast() + getattr() per review feedback.

features/steps/actor_loading_steps.py

@@ -9,6 +9,7 @@ from pathlib import Path
 
 from behave import given, then, when
 from behave.runner import Context
+from typing import cast
 
 from cleveragents.actor.loader import ActorLoader
 from cleveragents.actor.schema import ActorConfigSchema
@@ -451,8 +452,8 @@ def step_when_concurrent_list_actors_with_clear(
 @then("all concurrent list_actors calls should return consistent results")
 def step_then_concurrent_results_consistent(context: Context) -> None:
     """Verify that all concurrent list_actors calls returned consistent results."""
-    results: list[list[ActorConfigSchema]] = context._concurrent_list_results  # type: ignore[assignment]
-    namespace: str = context._concurrent_namespace  # type: ignore[assignment]
+    results = cast(list[list[ActorConfigSchema]], getattr(context, "_concurrent_list_results", []))
+    namespace = cast(str, getattr(context, "_concurrent_namespace", ""))
 
     # Each result should only contain actors from the requested namespace.
     # When clear() runs concurrently, some threads may see the full list while