The artificial-intelligence boom is sending Silicon Valley’s talent wars to new extremes. Tech companies are serving up million-dollar-a-year compensation packages‚ accelerated stock-vesting schedules and offers to poach entire engineering teams to draw people with expertise and experience in the kind of generative AI that is powering ChatGPT and other humanlike bots. They are competing against each other and against startups vying to be the next big thing to unseat the giants. The offers...