Silicon Valley’s artificial intelligence boom is spawning a new class of billionaires who are barely old enough to rent a car — but now rich enough to live large in California’s most lavish mega-mansions. Despite fears of a bubble, the AI market is poised to hit a fever pitch this year as San Francisco-based Anthropic plots an IPO at a valuation of $1 trillion or more. Even lesser-known startups and financial firms have raised billions as investors desperately try to cash in on the craze. More than 80 such AI billionaires exist on Forbes’ annual ranking of the world’s wealthiest people…