Manus, an artificial intelligence start-up, began with an idea among three engineers in Wuhan, China, united by an obsession with A.I. and a shared ambition to build a global venture. From the outset, they looked beyond China. Their big break came in March last year. Manus had drawn the attention of Silicon Valley investors with an A.I. agent capable of carrying out tasks on its own. By year’s end, Meta had agreed to acquire Manus. It looked like a clean breakout from China’s crowded, tightly regulated market and a path…