As a wall of television cameras shielded him from the icy wind, Eastern Washington football coach Beau Baldwin warmed up to the subject of life at the top. Moments after a 31-28 homecoming win over Sacramento State that was both exhilarating and confounding, Baldwin shrugged as if to say: That’s life in the Big Sky Conference. In their first game as the top-ranked team in the Football Championship Subdivision, the Eagles made just enough plays Saturday night to stay there for another week.