The last vestiges of the Trump presidency will be swept away on Wednesday, as the Bidens move into the White House. Desks will have been cleared out, rooms scrubbed clean and the president’s aides will be replaced by a new team of political appointees. It’s part of the massive transformation that a new presidency brings to the heart of government. Even in the best of times, the logistics of a transition are daunting, involving the transfer of knowledge and employees on a massive scale.