NEW YORK — Jonathan Majors’ ex-girlfriend Grace Jabbari broke down on the witness stand in Manhattan Thursday, after the Marvel actor’s lawyer made her repeatedly watch video of herself disoriented and injured from the morning after she says he assaulted her. Jabbari, 30, lost her composure during her third day of testimony at Majors’ Manhattan Criminal Court domestic violence trial, as she was grilled on exactly what she told police when they found her in the closet of Majors’ penthouse apartment in Chelsea. “I really don’t want to watch that video,” Jabbari said, as defense lawyer Priya Chau…