Plot: “Il Trittico,” Puccini's collection of three one-act operas. “Il Tabarro” concerns doomed lovers (Maria Guleghina, Salvatore Licitra); “Suor Angelica,” is about the salvation of a nun (Barbara Frittoli); “Gianni Schicchi” is a charismatic scoundrel (Alessandro Corbelli) out to steal a fortune willed to the church