There is, in "The Last Audition," something almost defiantly modest"a chamber piece of sorrow that refuses the grandiloquence of tragedy even as it circles one. The play, a solo vehicle of hushed ambitions, written by and starring Paul Shearman, sensitively directed by David St John, unfolds like a fading echo in an empty theater, its emotional register pitched not to catharsis but to the quieter, more unsettling key…