Wexford is to opera-goers what casinos are to gamblers. The uncertainty, the hope, the exhilaration — they’re all a crucial part of a festival that annually rolls the dice, plucking three obscure, often all but unknown, operas from the repertoire and giving them a staging. Dealing the cards is David Agler, the artistic director whose canny choices ensure that not only the house but also the audience always wins.