OTTAWA — Prime Minister Mark Carney triggered a national sprint Friday to redesign and rebuild 24 Sussex Dr., saying that the prime minister’s official residence is a national landmark that is now in critical condition. Speaking during a press conference in Ottawa at the dilapidated stone mansion that has been home to 10 Canadian prime ministers, Carney unveiled a new competition for Canadian firms to submit their rebuild and design proposals. The competition, which largely ends more than a decade of debate about where Canada’s prime ministers will live, will be led and largely judged...