fix(graders): preserve metadata from parent aevaluate call in RelevanceGrader

Address review feedback: preserve result.metadata from super().aevaluate()
to avoid losing important evaluation details from the LLM.

Author: XiaoBoAI

openjudge/graders/common/relevance.py

@@ -10,7 +10,7 @@
 
 from loguru import logger
 
-from openjudge.graders.base_grader import GraderMode, GraderScore
+from openjudge.graders.base_grader import GraderError, GraderMode, GraderScore
 from openjudge.graders.llm_grader import LLMGrader
 from openjudge.models.base_chat_model import BaseChatModel
 from openjudge.models.schema.oai.message import ChatMessage
@@ -315,19 +315,19 @@ async def aevaluate(
                 context=context,
                 reference_response=reference_response,
             )
-            score = result.score
-            reason = result.reason
+            return GraderScore(
+                name=self.name,
+                score=result.score,
+                reason=result.reason,
+                metadata=result.metadata,
+            )
 
         except Exception as e:
             logger.error(f"Error evaluating relevance: {e}")
-            score = 0.0
-            reason = f"Evaluation error: {str(e)}"
-
-        return GraderScore(
-            name=self.name,
-            score=score,
-            reason=reason,
-        )
+            return GraderError(
+                name=self.name,
+                error=f"Evaluation error: {str(e)}",
+            )
 
 
 __all__ = ["RelevanceGrader", "DEFAULT_RELEVANCE_TEMPLATE"]