By Pat Forde With determination and an unwavering positivity, the first-year head coach has silenced his critics as North Carolina prepares to play rival Duke in the national semifinals. After the first question of the postgame press conference, Hubert Davis’s pause lasted a full 15 seconds. Long enough to wonder whether the Zoom connection had frozen. Long enough to wonder whether the North Carolina coach had any answer at all, literally or figuratively. This was Feb. 16, after Davis’s Tar Heels had been embarrassed at home by a Pittsburgh team that would go on to lose 21 games and finish 13t…