WASHINGTON — With just two days to spare, President Joe Biden signed legislation on Saturday that lifts the nation’s debt ceiling, averting an unprecedented default on the federal government’s debt. The White House announced the signing, done in private at the White House, in an emailed statement in which Biden thanked congressional leaders for their partnership. The Treasury Department had warned that the country would start running short of cash to pay all of its bills on Monday, which would have sent shockwaves through the U.S.