The Big East is going through another painful breakup. San Diego State joined the list of schools leaving the conference (here’s a roundup) Wednesday, announcing its football program would remain in the Mountain West along with the rest of its sports in 2013. SDSU had committed to join the Big East as a football-only member; instead, it’ll be the third school — along with Boise State and TCU — to leave the conference without playing a conference game. Navy’s been an interested spectator throughout this process, watching its future conference add and subtract teams before the Mids join up as…