For employers banking on a surge of workers returning to the office this summer, Microsoft would like a word. The Redmond, Washington, tech giant, which has probably gamed out the back-to-office challenge as carefully as any organization, says the stream of workers coming back to its own offices has grown steadily since April 4, when the company began requiring work to be in person at least 50% of the time unless employees have permission from their managers. “We can watch things like badging data, and it continues to go up for us,” says Jared Spataro, Microsoft’s corporate vice president of m…