Keystatic setup (scaffold-time, opt-in)

Adds an optional editor UI to the new-website Astro overlay. Opt-in: the default scaffold is CMS-free (Markdown-in-git is the workflow). Run this only when new-website §1 Q3 says a non-technical person edits after launch. Keystatic is git-based — it writes Markdown/Markdoc into the repo, so "data rests in your GitHub" stays literally true and the site stays free + static. (Keystatic is built by Thinkmill, the Keystone team.)

Prereq: the site uses Content Collections (new-website Q1) — Keystatic edits the files those collections read. If the site is flat pages only, add a collection first.

Local mode (what this skill wires up)

Edit via the dev server; Keystatic commits nothing on its own — you review and git commit/push, Cloudflare deploys. The admin runs in astro dev only; the production build stays fully static (no adapter, no auth, no server). Steps applied to the project: