The Telluride Film Festival is a ritual with a habit. Each Labor Day Weekend, the four-day gathering — which begins Friday, Aug. 30 and runs through Monday, Sept. 2 — has a way of upending notions of celebrity by swinging the spotlight from “fame” to craft and context. It’s not that the famous don’t make the pilgrimage to the former mining town beneath the unreal peaks of the San Juans.