Burlington — Thetford Academy senior Ian Weider grew into decathlon over the past two years. Now the University of Vermont may have to grow into watching Weider. Although a fine first day wasn’t enough to guarantee a title, Weider recorded his second runner-up finish in as many years in the boys’ half of the Jerry Jasinski Vermont Decathlon-Heptathlon Meet at UVM yesterday. Weider held a 213-point lead on Mount Mansfield’s …