There is little doubt that the main event this week is the opening of the final part of the Washington National Opera’s season. The company’s penultimate production, Leoš Janáček’s Jenůfa in a staging by David Alden, won the Laurence Olivier Award this year for best new opera production. For reasons beyond understanding, not a single performance has sold out, although this is likely to be the high point of the WNO season. Some people may…