By Michael Rosenberg Long known for his full-tilt attacks on the mountain—often to his body’s detriment—the reigning downhill champion at the 2022 Paralympics has learned to whistle (and joke) while he works. There is an excellent chance that, in Beijing, one of the best skiers in the world will use the moments before some of the biggest races of his career to crack a joke. Andrew Kurka does this by design. Sometimes he chats about the course with the folks working at the start. What he says doesn’t really matter as much as how he says it. He keeps it light, and though he is talking to others,…