fix: stop replaying OpenAI stream text

Avoid replaying buffered text at the end of OpenAI streams so text-only responses are emitted once while forced tool fallback behavior stays intact.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/main.py

@@ -650,9 +650,7 @@ async def v1_chat_completions(req: ChatCompletionsRequest, request: Request):
                             buffered_text_parts.clear()
                             yield f"data: {json.dumps(payload, ensure_ascii=False)}\n\n"
 
-                    if buffered_text_parts:
-                        for buffered_text in buffered_text_parts:
-                            yield _text_payload(buffered_text)
+                    if buffered_text_parts and forced_tool_name and saw_tool_call:
                         buffered_text_parts.clear()
 
                     done_payload = {