A Superior Court judge on Tuesday refused to release a third suspect charged with murder in the stray-bullet shooting of Robert Cuadra, the Paterson honors student who was killed while unloading groceries for his grandmother on Jan. 19. Kahaz Heron, 18, will remain locked up while the state prepares its case for the Grand Jury. Heron, of Clifton, is one of three men arrested by Paterson police in a stolen car with two guns about 3 1/2 hours after what authorities say was a wild shootout between gangs on Godwin Avenue in which Cuadra was struck in the head with a stray bullet. Judge Joseph Port…