fix(translator): strip client_metadata when converting openai-responses to openai

client_metadata is an OpenAI Responses API-specific field. When translating
openai-responses requests to openai (Chat Completions), it leaked through
to providers like NVIDIA, which rejected it with a 400 "Unsupported
parameter". Strip it in the Responses-specific cleanup block alongside
input, instructions, store, and reasoning.

open-sse/translator/request/openai-responses.js

@@ -189,6 +189,7 @@ export function openaiResponsesToOpenAIRequest(model, body, stream, credentials)
   delete result.prompt_cache_key;
   delete result.store;
   delete result.reasoning;
+  delete result.client_metadata;
 
   return result;
 }