The D.C. Council voted to reject a baseball stadium lease agreement last night, then reconsidered four hours later and approved the deal after a plea from Mayor Anthony A. Williams and a threat from Major League Baseball President Robert A. DuPuy. The dramatic about-face came at 12:40 this morning after the council added its own price cap to the lease, limiting the District’s spending to $611 million for the project along the Anacostia River in Southeast Washington. With the cap in place, the council voted 9 to 4 for emergency legislation that approved the lease deal. It was not clear whether baseball would endorse the spending cap, but Williams’s aides said the mayor supported the council’s final plan. … Council members have expressed alarm over the city’s liability for increasing project costs. Although the council approved a $535 million stadium financing package in December 2004, recent estimates from city financial officials put the cost at $667 million.