ARLINGTON—Dezmon Jackson came up inches short on a desperate, fourth-down dive in the final seconds for Oklahoma State, knocking the fifth-ranked Cowboys out of contention for a spot in the four-team playoff. “Just heartbreak,” Cowboys guard Josh Sills said. Baylor safety Jairon McVea knocked Jackson out of bounds without letting him reach the pylon with 24 seconds remaining in the Big 12 championship game Saturday, preserving a 21–16 victory for the ninth-ranked Bears a year after they won only two games in coach Dave Aranda’s debut season. “This moment is something they can never take away,” Bears linebacker Terrel Bernard said. After the Bears (11–2, CFP No. 9) won their third Big 12 title, they didn’t get the chaos needed for them to have a chance to make the final four for the first time in the College Football Playoff rankings Sunday. Aranda recalled Oklahoma State coach Mike Gundy telling …