Director and writer Tina Landau in rehearsals for the Broadway revival of Floyd Collins . “My body of work has been a surprising mirror back to myself,” she says. Photo: Marc J. Franklin In the semi-twilight of tech rehearsal at the cavernous Vivian Beaumont Theater at Lincoln Center, Tina Landau is scrutinizing the movement of lanterns. Unassuming in a flannel shirt and beanie, the director’s watching her ensemble work through a scene change of Floyd Collins , the musical she wrote three