Lazy Training a Yat Network in JAX/Flax NNX

A runnable companion to the lazy-training post: the Yat layer with its frozen softplus scalars, the one-line NNX filter that trains a readout while the bank stays frozen, the per-arm learning-rate bracketing, and the movement telemetry that caught the anti-lazy power law. With the run's own prototype trajectories: a Gram matrix crystallizing as neurons accumulate, two readouts racing on frozen…