ZHANGJIAKOU, CHINA — After months of headlines about coronavirus tests, travel logistics and geopolitics, Beijing’s Olympic cross-country skiing venue, on the eve of its first competition Saturday, has emphatically changed the subject. To the winds of Zhangjiakou. Icy gusts billowed athletes’ training bibs, filled the resort town’s immaculately groomed ski tracks with dry, squeaky powder and generally consumed everyone’s attention Friday — from the team members who shielded their faces with buffs and layers of...