In a conference call with the Bay Area media, the Chiefs’ quarterback was asked if the four-year, $68 million contract extension he signed in August gave him assurance Kansas City was committed to him well into the future. [...] on Oct. 29, 2012, in his last full game with the 49ers, Smith completed 18 of 19 passes and tossed three touchdowns in a 21-point road win at Arizona. [...] when a concussion forced him to leave a game the next week, Smith led the NFL in completion percentage and ranked third in passer rating for a 6-2-1 team. Like Smith, he was a former first-round pick who endured cascades of catcalls from the fans of the team that drafted him (the Bears) and, ultimately, moved on. On Wednesday, Harbaugh, who played for four franchises in his career, acknowledged games against teams that had turned him loose were extra intense: “It added to the competitiveness,” he said to the Kansas City media. In 2012, after he learned just how fragile starting spots can be, Smith declined to divide a locker room that included veterans who wanted him to stay their starter. In exchange for quarterback Alex Smith, the 49ers received a 2013 second-round pick and a conditional 2014 selection that became a second-rounder. After a series of draft-day trades, they have netted three players and a 2015 draft pick from the swap with the Chiefs: The 49ers also used a 2013 seventh-round pick, obtained from the Titans in the 2013 trade involving the second-round pick from the Chiefs, as currency to move up five spots and select OLB Corey Lemonier in the third round in 2013.