WASHINGTON — When President Donald Trump watched a live feed of the U.S. military operation that captured Venezuelan President Nicolás Maduro, the director of national intelligence, Tulsi Gabbard, was not in the room. Just two days earlier, she had posted photos of herself on a beach in Hawaii at sunset practicing yoga, sending out a new year’s greeting for “peace.”That she appeared to be on vacation in the run-up to such a high-stakes, ultra-sensitive military operation seemed to underscore the extent to which she has been sidelined by the administration.But there she was on Wednesday, at an election center in...