This season has been a divisive slow burn of mounting pressure, but Euphoria finally produces its diamond in “Stand Still Like the Hummingbird,” a raw and sobering 24-hour escapade anchored by an extraordinary performance by Zendaya. I think the notion of an entirely Rue-centric episode will be frustrating to those who have been eagerly waiting for something (God, anything, please) to happen to Fez, Kat, and every other underdeveloped storyline this season — but this was the…