When the American Indian Film Festival opens Friday in San Francisco, it will be 31 autumns old. And like the season it is celebrated in, the festival showcases films that fall from a world warm with history while facing an industry that can be cold and cynical. Opening this year's festival will be "The Velvet Devil," showing at the Lumiere Theatre along with two other films: "Teachings of the Tree People," and "The Battle of Peter LeFarge." Delfin Vigil reports.