Target Margin Theater proudly boasts that Show/Boat: A River, its small-scale and bare-bones staging of Show Boat (at the Skirball Center on Washington Square through the 26^th), is a “bold reimagining” of the classic Jerome Kern & Oscar Hammerstein show, a “new adaptation that explores America’s transformation from the Jim Crow 1880s to the Chicago of the Great Migration to the challenges of today,” but I don’t see it.