Another round of unconfirmed reports about a potential U.S.-Iran diplomatic breakthrough sent fresh optimism rippling through oil markets on Monday, after Al Arabiya claimed that a Qatari-Pakistani mediation proposal had revived serious negotiations over Tehran's nuclear program. Citing unnamed sources, Al Arabiya reported that Washington was prepared to allow Iran to continue enriching uranium to 3.67%, with Tehran supposedly agreeing to the proposed limit. The sources suggested that a preliminary agreement was increasingly likely, although neither…