Qatar’s ruler met Iranian President Ebrahim Raisi in Tehran Thursday, state television reported, as talks falter on bringing Washington back into a 2015 nuclear deal between Tehran and major powers. The one-day visit by the emir, Sheikh Tamim bin Hamad Al-Thani, came as the European Union’s coordinator for the nuclear talks, Enrique Mora, held a second day of meetings in Tehran with Iran’s chief negotiator Ali Bagheri. Qatar, a close US ally, has added the Iran nuclear dispute to the list of diplomatic hotspots where it has sought to play a behind-the-scenes mediating role, and the emir has ca…