Rather than taking a seat among the senior staff who attended, Mr. Spicer, who spent much of the day in his office with the door closed, emerged suddenly in the White House colonnade to give reporters updates on when the news conference would begin. As soon as it did, he stood off to one side watching the proceedings next to a line of hedges, like a wedding planner who was dropped before the big event and nonetheless showed up to watch it unfold. Mr. Scaramucci did not attend.