Now the neighborhood is one of the city’s richest residential districts and hosts its most vibrant cluster of commercial art galleries — a status that the arrival of Marian Goodman cements. Though it’s a five-story, 19th-century warehouse tower of classic downtown Manhattan cast iron, its multimillion-dollar renovation by studioMDA is restrained. Walls are white, ceiling beams are black, and unlike some of its Chelsea peers, this is a gallery building that never feels like a spa or corporate headquarters. What it does feel like is the end of an era — and, with any luck, the beginning of a new one.