At the Kennedy Center on Friday night, violinist Jennifer Koh gave her first performance on the Terrace Theater stage as artistic director of the Fortas Chamber Music Series, which this season has hosted violinists Augustin Hadelich and Maxim Vengerov, a farewell from the Emerson String Quartet and a recital from bass-baritone Bryn Terfel. Still, if you’re a Fortas faithful, Friday’s program may have triggered déjà vu.