The day’s forecast called for high winds, but around midday in downtown Manhattan, it felt like a perfect spring day. The sun shone high in the sky last Tuesday as people gathered on the sidewalk around the corner from City Hall. Municipal employees mingled about, chatting excitedly. The cause for celebration wasn’t the weather — but a sleek, modernist-looking shed on the sidewalk where there had once stood a vacant newsstand.   The structure may not have looked like much, but it had been years in the making. Since 2021, Los Deliveristas Unidos — a union of app-based delivery workers — has been campaigning for the city to build outdoor structures where these workers can safely rest on the job, charge their e-bike batteries, and escape the elements.…