Ten months after successfully negotiating Yahoo’s $4.5 billion sale to Verizon, Marissa Mayer is back with a new venture — a technology incubator in downtown Palo Alto that will focus on consumer media and artificial intelligence. “Thinking about what's next, I returned to my roots, rented the original Google office where I started my career, and founded a lab with my longtime friend and teammate [Enrique Muñoz Torres],” Mayer tweeted late Wednesday. Mayer and Torres are launching Lumi…