WASHINGTON — Deal-maker Donald Trump has lived his life as one long negotiation, going with his gut and winging it when necessary. Should Trump become president, the White House could well be transformed into the world’s highest-profile improv club. It’s part of what delights his followers and horrifies his critics. All of it would run smack up against the stuffy traditions of a government structured to rein in the power of the individual. Among the leadership traits Trump would bring with him to the presidency are impulsivity.