“[The John Adams opera] is usually staged as an array of physicists and military generals standing around the New Mexico landscape, wondering if the first atomic bomb will ignite the entire planet – and looking worried. ‘But who wants to watch that?’ said R.B. Schlather.” David Patrick Stearns talks to the director about the staging he’s helming this week in Philadelphia. (Oh, and the singer playing Oppenheimer is a barihunk.)