NEW YORK — Former President Donald Trump was on and off the witness stand at a jury trial Thursday in less than 3 minutes but not before breaking a judge’s rules on what he could say by claiming that a writer’s sexual assault allegations were a “false accusation” and he wanted to defend himself and the presidency.Judge Lewis A. Kaplan swiftly instructed jurors to disregard those remarks from Trump, who didn’t look at the jury when he approached the witness stand, when he testified or …