Washington may be deserted this week, but there is still art to see. If you are stuck at work without much to do, ducking out early to hit some less-crowded galleries would be an excellent idea. Here a few things to help you conclude 2006. >> You have a couple weeks, through January 15, to see Ruth Duckworth, Modernist Sculptor, a selection of 80 ceramic pieces at the Renwick Gallery. Many of these works are…