DETROIT — Braden Montgomery had just hit a historic walk-off home run in his major-league debut against the Braves, the best team in baseball. White Sox manager Will Venable stepped to the podium to meet the media with his usual stoic look, but what he said belied it: “That’s a special debut. Needed it there on a day where situational execution honestly was a disaster.” Come again? “The first safety [squeeze bunt], we weren’t able to execute,” h…