Facing high-stakes brinkmanship as American warships and fighter jets mass off its shores, Iran has refused to concede to President Trump’s demands on its nuclear program and weapons — a stance that has bewildered U.S. officials. The authoritarian clerics who rule Iran see those concessions — which, in their view, could compromise their core ideology and sovereignty — as a greater threat to their survival than the risk of war. A dangerous mismatch in perceptions between Iran and the United States is why efforts to negotiate a deal over Iran’s nuclear and military capabilities look increasingly fragile, experts say, and a new regional conflict seems almost inevitable.