Photo by christaki In an email to staff Wednesday, Corcoran Gallery of Art and College of Art + Design director and president Paul Greenhalgh announced that he has tendered his resignation to the board of trustees. Greenhalgh, who will step down June 1, will continue to serve as the museum’s artistic director through a five-month transition period, and will remain an adjunct curator of European arts. On November 1, he will join the Sainsbury…