As Microsoft CEOs past and present gathered here to celebrate the company’s 50th birthday, one leader said he is targeting a particular metric’s improvement to guide his strategy on artificial intelligence. Mustafa Suleyman, chief executive of Microsoft AI, said his consumer and research division is tracking the usual measures of adoption for the company’s AI assistant called Copilot. In an older era when consumers gave less real-time feedback on software, the time they spent with a product — on social media, for instance — or the problems they could solve represented crude “proxies for quality,” he said.