banken-config

banken's typed config surface — ONE struct carrying both faces: `#[tatara(keyword = "defbanken")]` (the Lisp authoring face) and `impl shikumi::TieredConfig` (the deployment/tier-folding face). Follows the escriba-config precedent exactly: the shikumi tiers are the operator-facing runtime summary; the authored `.lisp` under `specDir` stays the load-bearing DOMAIN prescription (views/actions/columns/sort) that this struct cannot express.