Jazz chanteuse Risa Branch on animal-rights activism, switching genres, and the healing power of music — “I don’t know any jazz singers apart from you,” I tell Risa Branch as we peruse the dinner menu at Farmacy Kitchen, a pop-up vegan restaurant in SoHo. “You’re a kind of time traveler.” She may look like a 21st-century New Yorker — hair in long locs, an intricate silver…