From the top of the government, China is heavily promoting a plan to fix the country’s stagnant economy and offset the harm from a decades-long housing bubble. The program has a fresh slogan, presented foremost by Xi Jinping, the country’s top leader, as “new, quality productive forces.” But it has features that are familiar from China’s economic playbook: The idea is to spur innovation and growth through massive investments in manufacturing, particularly in high-tech and clean energy, as well as robust spending on research and development. And there have been…