Fix for Anthropic client class so system messages aren't lost

autogen/oai/anthropic.py

@@ -314,7 +314,7 @@ def oai_messages_to_anthropic_messages(params: Dict[str, Any]) -> list[dict[str,
     last_tool_result_index = -1
     for message in params["messages"]:
         if message["role"] == "system":
-            params["system"] = message["content"]
+            params["system"] = params.get("system", "") + (" " if "system" in params else "") + message["content"]
         else:
             # New messages will be added here, manage role alternations
             expected_role = "user" if len(processed_messages) % 2 == 0 else "assistant"