With its pastel green and yellow interior, its dazzling collection of Impressionist paintings, and long, low sofas that look like vintage Cadillac convertibles, Sunnylands was a Versailles for the Space Age. In Palm Springs, the mecca of midcentury modern architecture, this immaculately preserved estate is considered the undisputed masterpiece, envisioned by A. Quincy Jones, one of California's most important architects; and furnished by California's...