How to write a new styleKit look block (a wash, an ink, a paper, a hatching, a grain) that stacks, swaps and masks like every other block. It sets out the full shape every block follows: the folder layout, every `block.yaml` key, stacking in a slot (layer or chain, and rank), the extra inputs (the soft field, the pigment set, the rendered frame, the paper field and the scene's sun), per-block defaults so many blocks share one shader, pigment mixing, stable noise, the shared header, the `skCommon` helpers and `sk_finish`, reading the ground, the wobble, the clock and surface coordinates, publis…