From the earliest days of his campaign, Donald J. Trump made keeping manufacturing jobs in the United States his signature economic issue, and the decision by Carrier, the big air-conditioner company, to move 2,000 of them from Indiana to Mexico was a tailor-made talking point for him on the stump. On Thursday, Mr. Trump and Mike Pence, Indiana’s governor and the vice-president elect, plan to appear at Carrier’s Indianapolis plant to announce they’ve struck a deal with the company to keep a majority of the jobs in the state, according to officials with the transition team as well as Carrier....