NANTUCKET, Mass. — President Joe Biden appeared on the loose Friday in Nantucket. Biden spent more than an hour walking around downtown Nantucket’s cobblestone streets, popping unannounced into quaint mom-and-pop shops, appearing to make purchases and posing for photos with surprised business owners. He was accompanied by some of his grandchildren. Biden and his entire family are spending the Thanksgiving holiday on the Massachusetts island, renting a sprawling compound that belongs to his friend and billionaire philanthropist David Rubenstein. “Hey, Joe,” “We love you, Joe,” some people shouted as Biden passed by on a cold and rainy day.