SEATTLE—Uber has agreed to pay more than $3.4 million to 15,000 drivers after making mistakes related to Seattle’s pioneering paid sick leave law covering gig workers. Amid the COVID-19 pandemic, the Seattle City Council last year temporarily extended sick and safe leave protections to gig workers, who previously didn’t qualify because many companies treat them as independent contractors. The law allows the workers to accrue and take paid days off—based on their average daily compensation, including tips—to care for themselves or family members who get sick. The idea was to reduce the financial pressure on them to keep working, possibly spreading the virus, at a time when people were becoming more reliant on gig workers to perform tasks like grocery delivery. It also allows them them to take paid time off for other reasons, such as to seek help in domestic violence cases or to care for children whose schools …