MILAN — The manifesto that Sabato de Sarno supplied with his new collection for Gucci set him a trap in the sense that it created expectations that his own inclinations made it unlikely for him to meet. Coats are clearly his passion. It’s probably not a giant leap to imagine that the perfect coat might be his holy grail as much as the perfect sleeve was Cristobal Balenciaga’s. De Sarno suggested as much when he referred to the making of…