For decades, everything China wanted to do beneath the Pacific ran through a single facility, the Bohai shipyard at Huludao in Liaoning province. That constraint has now been removed. In late May and early June, commercial satellite imagery showed a roughly 120-meter submarine with an unusually small sail at a fitting-out basin at Jiangnan Shipyard in Shanghai, a yard known for destroyers and aircraft carriers, never before for nuclear boats. Na…