def retrieve_for_turn(history, question):
    stand_alone = llm_rewrite(history, question)   # 合并指代与上下文
    hits = retriever.search(stand_alone)            # 用改写后查询检索
    log(question, stand_alone, [h.id for h in hits])
    return hits

把用户最新问题改写为不含指代、可独立检索的问题；
保留专名与数字；只输出改写结果。