## Light header on top-level pages + chain-derived smoke + old-structure cleanup

- **One header theme everywhere.** Library, Partners, and Dev now use the same light header as the version pages — the dark page headers (where the new section links rendered as unstyled default buttons) are gone. One canonical block: white sticky bar, styled section/page links, switcher, demo button; brand and buttons no-wrap.
- **Smoke suite is chain-derived.** Section labels, the latest file, scroll targets, and switcher counts are computed from `versions.json` + the layered `site/menu.json` instead of hardcoded — a redesign no longer requires editing the smoke (frozen-version assertions stay literal, since frozen versions can never change). The host-default check is now byte-exact against the latest artifact.
- **Old-structure cleanup:** removed the stray `src/versions/…` template that survived the v0.5 merge (verified byte-identical to the chain's v0.4.2 template before deletion).