refactor: retire the hand-written site

Deletes the pre-Astro pages, scripts, and stylesheets that the migration
replaced, and moves the ones it did not replace out of the way.

Deleted (32 files): app.js, responsive.css, landing.css, rules/app.js,
rules/styles.css, skills/app.js, the ten route index.html files, and the
root hands-on/ copy, which is byte-identical to public/hands-on/ -- the
one the build actually ships.

Moved to legacy/ (12 files): styles.css, full-guide/audit.css,
chapters.css, skills/styles.css, skills-review/styles.css,
skills-review/change-lens.css, and the skills-review/app.js module graph.
These are not dead. The Astro pages import them and the build fails
without them, which the plan had not accounted for. They go to legacy/
rather than src/ because check-tokens.mjs sweeps src, and these files are
full of raw hex and unnamed breakpoints: moving one into src/ should mean
migrating it to tokens in the same change, not adding a scan exclusion.
The prettier, stylelint, and eslint ignore lists that already named these
files at their old paths now name legacy/ instead.

verify.mjs no longer reads app.js. The 102 Portuguese strings were
extracted from its translations.pt object before deletion into
.agents/snapshots/full-guide-pt.json -- a legacy capture, not a snapshot
of the Astro build, so the assertion still compares against an
independent source. The brace-matching helper's assertion is replaced by
one that rejects an empty snapshot entry, without which trimming the
snapshot would make the presence check pass vacuously. Count stays at 84.

audit-ui.mjs reads the ten pages from dist/ and resolves Astro's
base-absolute hrefs against it.

Before deleting anything, rendered-text-diff was run across all ten
routes plus both Portuguese pages: every one at parity, 0 missing and 0
extra. That comparison is not repeatable once the legacy files are gone.
computed-style-diff on /full-guide/ stays at 32 differences, so the moves
are style-neutral.

Docs updated to match: README, AGENTS.md, GATES.md, the architecture
context, the operations guide's lab instructions, and the three skills
that told you to serve the vanilla site.

Publishing is not part of this commit.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

plans/astro-refactor/task-20-cutover.md

@@ -57,3 +57,81 @@ git rev-parse origin/pages   # write it down
 - [ ] Old files deleted; `pnpm run gate` green
 - [ ] Docs match reality
 - [ ] Previous `pages` SHA recorded for rollback
+
+---
+
+## Cutover record
+
+`origin/pages` before cutover: **`37a1e480c6bffb0bff77ad3854ec068688c17d7b`**
+("Merge branch 'main' into pages"). Reset `pages` to this SHA to roll back.
+
+### Step 1 — verification before deletion
+
+`rendered-text-diff.mjs` compares the _rendered_ DOM of each legacy page against
+its Astro replacement. Deleting the legacy files makes that comparison
+impossible, so the full sweep was taken first, against the post-cutover build:
+
+| Route             | Legacy spans | Astro spans | Missing | Extra |
+| ----------------- | -----------: | ----------: | ------: | ----: |
+| `/`               |           36 |          36 |       0 |     0 |
+| `/full-guide/`    |          432 |         432 |       0 |     0 |
+| `/summary/`       |           34 |          34 |       0 |     0 |
+| `/models/`        |           36 |          36 |       0 |     0 |
+| `/agents/`        |           39 |          39 |       0 |     0 |
+| `/skills/`        |           48 |          48 |       0 |     0 |
+| `/rules/`         |          119 |         119 |       0 |     0 |
+| `/skills-review/` |          178 |         178 |       0 |     0 |
+| `/full-guide/` pt |          431 |         431 |       0 |     0 |
+| `/rules/` pt      |          119 |         119 |       0 |     0 |
+
+`computed-style-diff.mjs full-guide --widths 880,1050` → 32 differences,
+unchanged from the task 15e result, so the file moves below are style-neutral.
+
+### Step 2 — what could not be deleted
+
+The brief assumed every legacy file had been superseded. Seven had not: the
+Astro build still imports them, and `astro build` fails outright without them.
+
+| File                            | Imported by                       |
+| ------------------------------- | --------------------------------- |
+| `styles.css`                    | `src/pages/full-guide.astro`      |
+| `full-guide/audit.css`          | `src/pages/full-guide.astro`      |
+| `chapters.css`                  | `src/layouts/ChapterLayout.astro` |
+| `skills/styles.css`             | `src/pages/skills.astro`          |
+| `skills-review/styles.css`      | `src/pages/skills-review.astro`   |
+| `skills-review/change-lens.css` | `src/pages/skills-review.astro`   |
+| `skills-review/app.js`          | `src/pages/skills-review.astro`   |
+
+`app.js` pulls in `catalog.js`, `files.js`, and `vote.js`, which pull in
+`submitted-catalog.js` and `submitted-files.js` — twelve files in all.
+
+They were moved to `legacy/`, not into `src/`. `check-tokens.mjs` sweeps `src`,
+and these files are full of raw hex and unnamed breakpoints; moving one into
+`src/` should mean migrating it to tokens in the same change, never adding a
+scan exclusion. `legacy/` keeps the checker's scope honest and stops the files
+sitting at route-shaped paths next to the routes they no longer serve.
+
+Deleted outright (32 files): `app.js`, `responsive.css`, `landing.css`,
+`rules/app.js`, `rules/styles.css`, `skills/app.js`, all ten `index.html` files,
+and the root `hands-on/` copy — byte-identical to `public/hands-on/`, which is
+what the build ships.
+
+### Step 3 — verify.mjs off the legacy source
+
+Two assertions read `app.js` to parse `translations.pt`. The 102 strings were
+extracted verbatim before deletion into `.agents/snapshots/full-guide-pt.json` —
+a legacy capture, not a snapshot of the Astro build, so the check still asserts
+against an independent source.
+
+The brace-matching helper went with the file, taking one assertion. It was
+replaced by a check that no snapshot entry is empty: without it, trimming the
+snapshot would make the "every string is present" assertion pass vacuously.
+Count stays at 84.
+
+`audit-ui.mjs` now reads the ten pages from `dist/`, resolving Astro's
+base-absolute `/ai-for-dummies/...` hrefs against `dist/`.
+
+### Not done here
+
+Steps 3, 4, and 6 — publish, verify on the real host, fast-forward `pages` — are
+untouched. They need a human present.