The Signature wraps up its season with an exquisite bow in Tony Kushner’s fantastical tribute to the magic of theater, imaginatively adapted from Pierre Corneille’s proto-postmodern L’Illusion Comique (1636). Michael Mayer’s ripe staging invites a suspension of belief, abetted by ravishing design and a luxurious cast of eight (including Lois Smith and David Margulies).—Adam Feldman