Treasury Secretary Scott Bessent gave representatives of the so-called Department of Government Efficiency full access to the federal payment system late on Friday, according to three people familiar with the change, handing Elon Musk and the team he is leading a powerful tool to monitor and potentially limit government spending. The new authority follows a standoff this week with a top Treasury official who had resisted allowing Mr. Musk’s lieutenants into the department’s payment system, which sends out money on behalf of the entire federal government. The official, a career civil servant named David Lebryk, was put on leave and...