Dirar Abu Sisi, a Gaza engineer who disappeared in Ukraine in mid-February and surfaced in an Israeli prison, spoke to reporters for the first time while attending an Israeli court hearing to extend his detention. He said he had been kidnapped by Israel “for no reason.” Most details of the case are subject to a court-imposed rule of silence, but Israeli leaders say Mr. Abu Sisi, 42, is a member of Hamas who holds valuable information.