On September 24, the world's two most powerful leaders will meet at a White House transformed into a theater of statecraft, where polished granite and dress uniforms signal the weight of the moment even as the substance remains elusive. Donald Trump and Xi Jinping carry into their meeting a full ledger of unresolved tensions — artificial intelligence, trade, Iran, and Taiwan — each too politically charged for either side to yield ground. History has long known summits that accomplish less in their agreements than in their atmospheres, and this one may be remembered less for what was decided th