A newly listed oceanfront estate in Bridgehampton comes with both architectural pedigree and a backstory rooted in the art and diamond worlds of 1980s New York. The trophy Hamptons property at 15 Dune Road, now asking $45 million, was built by the late Ara Arslanian, a second-generation diamond dealer known not only for rare stones but also for his close ties to artists including Jean-Michel Basquiat,...