fix(test): resolve AmbiguousStep collision after master merge

Renamed 'listing actors with namespace' step in actor_loading_steps.py
to 'listing loaded actors with namespace' to avoid collision with
actor_registry_persistence_steps.py from master. Updated
actor_loading.feature to use renamed step.

features/actor_loading.feature

@@ -126,8 +126,8 @@ Feature: Actor registry and loader
       | ana.yaml        | assistants/analyzer  | llm  | gpt-4  |
     When I create an actor loader with that directory as search root
     And I run discovery
-    Then listing actors with namespace "assistants" should return 2 actors
-    And listing actors with namespace "utilities" should return 1 actors
+    Then listing loaded actors with namespace "assistants" should return 2 actors
+    And listing loaded actors with namespace "utilities" should return 1 actors
 
   # ────────────────────────────────────────────────────────────
   # Content hash caching

features/steps/actor_loading_steps.py

@@ -317,7 +317,9 @@ def step_then_get_none(context: Context, name: str) -> None:
     assert config is None, f"Expected None for '{name}', got {config}"
 
 
-@then('listing actors with namespace "{namespace}" should return {count:d} actors')
+@then(
+    'listing loaded actors with namespace "{namespace}" should return {count:d} actors'
+)
 def step_then_list_by_namespace(context: Context, namespace: str, count: int) -> None:
     loader: ActorLoader = context._loader
     actors = loader.list_actors(namespace=namespace)