fix(11153): resolve lint failure and revert conflicting registry change

- Format auto_debug.py per ruff to fix CI / lint failure
- Revert registry.py provider/model model-field change that conflicts with TDD test assertions from issue #10926 (models must use bare identifiers without provider prefix)

src/cleveragents/actor/registry.py

@@ -129,7 +129,7 @@ class ActorRegistry:
         yaml_dict: dict[str, Any] = {
             "name": self._actor_name(provider, model),
             "type": "llm",
-            "model": f"{provider}/{model}",
+            "model": model,
             "description": (
                 f"Built-in actor from provider registry ({provider}/{model})"
             ),

src/cleveragents/agents/graphs/auto_debug.py

@@ -302,9 +302,7 @@ Validate this fix."""
                         for word in ["valid", "correct", "resolves", "fixes"]
                     )
         except Exception as exc:  # pragma: no cover - defensive
-            logger.warning(
-                "LLM validation failed, treating fix as invalid: %s", exc
-            )
+            logger.warning("LLM validation failed, treating fix as invalid: %s", exc)
             is_valid = False
 
         if not is_valid: