When President Xi Jinping of China convened a group of top officials to discuss the economy last month, the highly publicized meeting was seen as a moment of triumph. A stock market plunge last summer, and a messy currency devaluation that followed, had faded from global view. In the relative calm, he seemed to usher in a new era of economic management, promising policy coordination at the highest levels to prevent another bout of turmoil. Less than three weeks later, his plans have been derailed as China’s stock market and currency once again rattle investors around the world. The latest rout sets up a challenge for Mr. Xi, who has positioned himself […]