The United States and Iran reached a deal Sunday to halt more than three months of war, but it did little to bring a permanent solution to a conflict that has rattled the global economy and tested the limits of American power. The agreement, a memorandum of understanding, establishes a 60-day ceasefire across the Middle East, reopens the Strait of Hormuz, ends dueling Iranian and American blockades of the waterway, and releases billions in frozen Iranian funds.