ALBANY — Outgoing State University of New York Chancellor Nancy Zimpher has agreed to stay on the job through the summer until the incoming chancellor, Kristina Johnson, is able to start Sept. 5. Zimpher had announced last year her plan to retire from the 64-campus system on June 30. The SUNY board of trustees, meanwhile, had planned to appoint an interim leader to oversee operations for the two months between her departure and Johnson's arrival.