For more than a century, the pages of Architectural Digest magazine have captured not only timeless designs but also the spirit of their subjects’ homes. Their distillation of private spaces is featured in a new book, “AD at Home: Architectural Digest.” Serena Altschul talks with editor Amy Astley about the magazine’s treatments; and with actor Live Schreiber and designer Marc Jacobs about what it means to open up one’s living space to the magazine’s photographers.