Like many 12-year-olds, Hannah Yarbrough’s teeth are wrapped in corrective braces. Despite its metal and plastic confines, the rising eighth-grader’s smile lights up a room.That smile, combined with her sunny disposition and unusually mature sense of compassion, have been reaching many this summer. The North Forsyth Middle School student decided she didn’t want to spend her break in the traditional fashion of hanging out at the pool or going to the mall with friends.