FARGO, N.D. — Paige Halder called the introduction to her new event — the seven-pronged heptathlon — “a little rough.” Done by the heptathlon athlete in the same meet are the 100 meters, the high jump, the shot put, the 200 meters, the long jump, the javelin throw and the 800 meters. Those seven events are done over a two-day period. The heptathlon is done outdoors. During the indoor season the javelin and 200 are left off the list, it’s done in…