The dizzying events of the past week have pushed to the sidelines the congressional squabbling over President Biden’s domestic agenda, and are already redefining the arc of his presidency.WASHINGTON — Ron Klain, the White House chief of staff, gave a pep talk early on Feb. 18 at the daily gathering of the president’s most senior aides: The next 10 days, he said, will be the most consequential of the Biden presidency.President Biden’s military and intelligence chiefs had told him that a Russian invasion was all but inevitable. Mr. Klain, a veteran of Washington and one of Mr. Biden’s closest advisers,...