The big business and entertainment headline Thursday morning involved Disney purchasing 21st Century Fox, the Rupert Murdoch media conglomerate. The all-stock price tag — valued at $52.4 billion — means Disney is making a big bet on media. Of particular interest to local sports fans, though, is a part of the deal that might get lost in the bigger headline. In the deal, Disney — the parent company of ESPN — bought all of Fox’s regional sports networks.