The sight unnerved Rusty Kuntz as he entered the visitors’ clubhouse at Fenway Park on July 20. The KC Royals had dropped their third game in a row and fallen below .500 for the first time in a month, but a collection of players were focused on their iPads, playing a game called “Clash of Clans.” A series of meetings followed, and the Royals became more focused and evolved into a well-oiled machine built for October.