Proves the no-build ESM path: import { Button } from "_esm/cs.mjs" self-ensures React (pinned, skipped when present), side-loads the compiled bundle once, resolves the namespace by prefix, and re-exports every component. Asserts export/manifest parity (a new component without a regenerated _esm/cs.mjs fails here) and that a mounted Button still receives brand tokens. Verdict on window.__esm.