(Credit: KarenAlmond/Metropolitan Opera) A “shabby little shocker.” That’s how musicologist Joseph Kerman described Puccini’s “Tosca.” Shabby? No. A little shocker? No. It’s a big shocker. Perhaps we’ve become inured to how dark and violent “Tosca” is with scenes of rape, murder, torture, and suicide. There was no mistaking the grittiness of Puccini’s fast-paced thriller at the Metropolitan Opera. The October {…}