SAN ANTONIO — Somehow, some way, the San Antonio Spurs seem to have discovered a secret that every team in the league desperately searched for all season long. They have figured out a way to slow down LeBron James.Whether it’s Kawhi Leonard’s incredible wingspan, Danny Green’s dogged determination or a stash of kryptonite that Tim Duncan happened upon while taking a walk along the banks of the San Antonio River, it’s working. And yet the Spurs return home for Game 3 of the NBA Finals tonight at 8 perhaps feeling lucky to have earned a split in Miami.