President Biden and China’s leader, Xi Jinping, face a host of thorny geopolitical issues as they meet Wednesday in San Francisco: trade, Taiwan and the war between Israel and Hamas. But they have found some common ground in the cultural sphere. Both leaders have in recent days praised the visit by a delegation of Philadelphia Orchestra musicians to China. The musicians arrived there last week to mark the 50th anniversary of the orchestra’s celebrated 1973 visit to Beijing, when it became the first American ensemble to perform in Communist-led China…