Math: Robust statistics

Quantile-space Huber-Wasserstein loss

For models that predict probability distributions, replace the usual Wasserstein-2 loss or a Huber penalty on the final Wasserstein distance with a Huber penalty on quantile-by-quantile prediction errors. This suppresses gradients from localized outliers while retaining quadratic gradients on the majority of the distribution, which is useful for uncertainty prediction, histogram prediction, and distributional distillation.