Power was shut off in Nicasio, the San Geronimo Valley and Stinson Beach for a day this week, as PG&E aims to reduce the fire threat by de-energizing when the weather is risky. The utility fulfilled its goal of making the shutoffs far shorter and less widespread than they were last year, when all of Marin lost power for four days. The impact was still pervasive: Schools and businesses were closed, food was spoiled, and…