At a rooftop bar on Manhattan’s Lower East Side, roughly 150 quant researchers met with employees at the artificial-intelligence startup Anthropic who implored them to consider a life away from Wall Street.Over plates of potstickers and popcorn chicken, they rubbed shoulders at the June mixer with former hedge fund quants-turned-Silicon Valley evangelists who encouraged them to apply for jobs at Anthropic, according to the company. This month, the San Francisco-based firm is going global with an...