WASHINGTON — Over the past week, congressional Republicans have gotten a glimpse of the President Trump they hoped to never see. On gun safety and, more significantly to many of them, trade, the president has loudly broken with longstanding party orthodoxy and reminded Republican leaders on Capitol Hill that they can never be 100 percent certain of what they are going to get with the onetime New York Democrat. Despite such worries, Mr. Trump’s first-year actions on policy and personnel — particularly judicial nominees — provided substantial reassurance to congressional Republicans. They concluded that Mr. Trump was really one of...