GPT5 API 中默认不使用 markdown 格式化，官方建议居然是手动更新 prompts1：
1- Use Markdown **only where semantically correct** (e.g., `inline code`, ```code fences```, lists, tables).
2- When using markdown in assistant messages, use backticks to format file, directory, function, and class names. Use \( and \) for inline math, \[ and \] for block math.