Architect Neal Schwartz didn’t set out to startle the neighbors when he designed a 390-square-foot addition to his Sonoma vacation retreat during the pandemic. Yet the principal of S^A | Schwartz and Architecture is a little gleeful about combating the endless ranks of “modern farmhouses” in California wine country with the 18-foot-tall protuberance that rises like an airplane tail from the end of the flat-roofed, minimalist house he designed for himself and his husband in 2012.