The current production of Tosca at the San Francisco Opera is wonderful to hear. The orchestra plays lavishly and the excellent double cast (which featured Patricia Racette in the title role, Brian Jagde as Cavaradossi and Mark Delavan as Scarpia the night I saw the show) perform with utter conviction.If only this Tosca could be as easy on the eyes as it is on the ears. I don't think I've ever been forced to sta…