Cannes: Koreeda begs us not to delegate our imaginations to AI in a winsome grief drama that lacks feeling. A master sentimentalist like Hirokazu Koreeda riffing on a movie as soul-obliterating as Steven Spielberg’s “ A.I. Artificial Intelligence ” sounds like a surefire recipe for the tear-jerker of the year, so I was surprised to discover that “ Sheep in the Box ” is one of the most emotionally stunted dramas the “Monster” auteur has ever made.  To some extent, that’s by design, as the