Include messages in ConversationLog.to_dict() for report conversation examples

Without this, the training report's example conversations section would
have empty message histories since evaluate_prompt() calls to_dict().

https://claude.ai/code/session_01DPirJ78YYN4fJUvUFJ5D6V

layer0/reward.py

@@ -78,6 +78,7 @@ class ConversationLog:
             "customer_persona": self.customer_persona,
             "true_intent": self.true_intent,
             "agent_intent": self.agent_intent,
+            "messages": self.messages,
         }