“By acknowledging a massive mistake and moving past one of the most scrutinized draft decisions in recent memory in a deal completed a few hours before the start of the Niners’ preseason finale against the Chargers at Levi’s Stadium, coach Kyle Shanahan drained at least some of the drama from what had been a long, hot summer. As one AFC head coach put it to me Friday morning: “For a team with Super Bowl aspirations, there’s a lot of noise coming from that place, and I don’t think that’s particularly healthy.