WEST PALM BEACH, Fla. — Kellyanne Conway, the Republican pollster and strategist who helped guide President-elect Donald J. Trump to victory in November, will be appointed counselor to the president, becoming the highest-ranking woman in his White House, the transition team announced early Thursday. Ms. Conway, who took over as campaign manager shortly after Mr. Trump clinched the Republican nomination over the summer, guided her candidate through a brutal and divisive campaign, often appearing on television to vouch for him during periods of scandal or controversy.