SOUTH LAKE TAHOE, Calif.—Connor Jones sunbathed with his dog on the otherwise empty beach at Ski Run Marina on Monday, as residents trickling back into town filled up their cars at a gas station behind him and employees of a water sports rental company docked jet skis and boats they had anchored away from the shores of Lake Tahoe to prevent them from igniting from wildfire. He and others living in the resort city of South Lake Tahoe breathed a collective sigh of relief on Sunday when officials downgraded a mandatory evacuation order put in place a week ago to a warning. “I figure they wouldn’t take repopulation lightly and, if they made the decision to allow people to come back, then they were probably confident that they’re not going to have any issues,” he said. When the Caldor Fire gobbled up pine trees and crossed the Sierra Nevada last …