The hearse carried only a wreath, because technically, the dearly departed was still alive — albeit barely, considering the vegetative, life-supported state the Corcoran Gallery of Art has been in since August. When the institution’s takeover by the National Gallery of Art and George Washington University was approved last month, the spirit had already left the body. So on Saturday, the day before the museum was scheduled to close for renovations, from which it will later emerge as part of the National Gallery of Art, former staff members gathered there to mourn.