Marylebone theatre, LondonRussian director Alexander Molochnikov's play within a play raises vital questions about the cost and creativity of exile but is undone by its own cleverness This is a play about the making of a play in a time of war. The latter is Anton Chekhov's The Seagull, and a fictional director, based on a real-life director, is producing it when Russia declares war on Ukraine. If that sounds like met…