fix：Jev 观测改为 evaluator，会话视图不再被 JSON 分类结果占位

app/clients/decision.py

@@ -63,8 +63,8 @@ class DecisionEngine:
         from app.observability.tracing import observe_decision, record_decision
 
         # 观测包在请求外面：成功才记结果，失败仍抛原来的 DecisionError
-        # generation 为 None 时 record_decision 什么都不做
-        with observe_decision(request) as generation:
+        # observation 为 None 时 record_decision 什么都不做
+        with observe_decision(request) as observation:
             try:
                 response = await client.system_one(
                     state=request.state,
@@ -93,7 +93,7 @@ class DecisionEngine:
             except TypeSafeError as error:
                 raise DecisionError("Jev SDK 调用失败", kind="sdk") from error
             parsed = self._parse_response(request, response)
-            record_decision(generation, parsed)
+            record_decision(observation, parsed)
             return parsed
 
     @staticmethod