Massachusetts' top historic preservation officer has dealt a setback to the proposed Nantucket Sound wind farm, ruling yesterday that the body of water is eligible for listing on the National Register of Historic Places because of its cultural significance for two Native American tribes. In a letter released late in the afternoon, Brona Simon, state historic preservation officer, said she believes that Nantucket Sound is so culturally important to two Wampanoag tribes that it should be eligible to be listed on the National Register as a traditional cultural property.