Donald Trump returned from Beijing calling his two-day summit with Xi Jinping a "success,” but the rare earth market is less convinced. Despite closely watched talks on May 14-15, no formal agreement emerged on China's export controls, and shipments of the critical heavy minerals that power everything from F-35 fighters to electric vehicles remain well below historical levels. That is the assessment from BMI, the Fitch Group research unit, which said China's stranglehold on global rare earth supply is expected to "stay firmly in place"…