Python: OpenAIChatClient (Responses API) does not implement service_url(), so server.address is reported as Unknown #9224

RawOpenAIChatClient does not override BaseChatClient.service_url(), so spans from OpenAIChatClient and the Foundry chat clients built on it report server.address as "Unknown".

OpenAIChatCompletionClient and OpenAIEmbeddingClient already return the underlying client's base_url. The Responses client can do the same.

Related: #6626, #9221 (same gap in the Ollama chat client). I have a small fix ready.