Federal officials designated a large swath of ocean about 14 miles south of Martha’s Vineyard yesterday as the potential site for a massive wind farmthat would dwarf Cape Wind, the long-stalled project that is planned for Nantucket Sound. After two years of meetings with local and state officials, environmental groups, and others, including local tribes, officials at the US Bureau of Ocean Energy Management said they are launching an environmental assessment of about 1,300 square miles that could give rise . . .