The newest addition to Seabourn’s fleet, the sumptuous, 600-passenger Seabourn Encore is also the luxury line’s biggest, although still petite in cruising terms, at 40,340 tons. The all-inclusive ship has the feel of a luxurious private yacht, all curves, rich blues, gleaming mahogany and polished stainless steel. She is stylish and contemporary, effortlessly classy but…