Editing a Deep Equilibrium Network, in JAX/Flax NNX

A runnable companion: build the weight-tied Yat equilibrium operator in Flax NNX, then teach a class by appending rows to the readout (F untouched, exact) or into the shared dynamics (one paste, present at every depth), measure the contraction certificate with power iteration and bisect one gain to restore it, audit the drift of 520 old fixed points, watch a layer-only edit evaporate, and forget…