Jared Kushner is emerging as the smoothest, slickest operator in the Court of King Donald. He is also, by far, the busiest — and the hardest to fire. President Trump is apparently convinced that his son-in-law, who serves officially as a senior adviser, can fix anything. Make that everything: In less than three months, Trump has given Kushner, 36, the following assignments: • Reinvent the federal government, one of the biggest and most complex organizations in the world. As head of the “White House Office of American Innovation,” Kushner is supposed to bring the mindset and practices of the business...