For weeks, the parameters of a preliminary agreement to end the war between the United States and Iran have been clear to its negotiators. The hang-up? How to devise a deal so each side can claim a win. 几周以来，结束美伊战争的初步协议框架对双方谈判代表来说已经非常明确。症结在于如何设计一项协议，让双方都能宣称自己是赢家。…