The concrete, Manhattan sidewalk in the middle of February — which vacillates between a rainstorm and an arctic wind tunnel, depending on the time of day — is the true cool-girl runway. New York Fashion Week is just getting started, yet the streets are already chock full of magazine editors and Instagram models, stepping out from designer shows to their Uber cars in the most creative, layered ensembles — pairing a cropped puffer coat with open-toed sandals and topping it all off with a velvet headband.