On a scorching morning in Beijing, Hao and a dozen other food delivery drivers sweltered outside a hot-pot restaurant. They smoked. They swiped through videos. They waited for the next round of lunch orders from people wise enough to stay indoors.Hao, like most of China’s 200 million gig workers, is eligible by law to receive a “heat wave allowance,” or danger money for those required to work for hours in extreme heat conditions. He should be paid at least 180 yuan ($25) per month when the heat ...