By Albert Breer The 49ers outbid their rival for the former Panther, who surprised Kyle Shanahan with how quickly he could learn the team’s offense. It was early the morning of Oct. 21 when Kyle Shanahan bumped into his assistant head coach, Anthony Lynn, at the 49ers’ practice facility. The Christian McCaffrey trade had happened hours earlier, and the place was buzzing. But for the time being, Shanahan figured his excitement needed tempering since he had to prepare for the Chiefs, and McCaffrey, presumably, wasn’t going to play. Then, Lynn recounted his conversation from overnight with McCaff…