A White-Box DeepSurv, in JAX/Flax NNX

A runnable companion: the Cox partial-likelihood loss, a standard DeepSurv, and a Yat-kernel DeepSurv whose log-risk decomposes into prototype patients, all in Flax NNX. Concordance evaluation, exact convex attribution, cohort deletion, and OOD abstention as short array operations. Every number is from a real run on METABRIC breast-cancer survival.