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>

.stylelintignore

@@ -7,23 +7,16 @@ public/submitted-skills
 skill-reviews
 vote-service
 
-# Legacy site sources, slated for deletion at cutover (task 20). Same list and
+# Unmigrated legacy stylesheets, kept verbatim under `legacy/`. Same list and
 # same reasoning as .prettierignore: these are minified, single-line
 # stylesheets. stylelint's `declaration-block-single-line-max-declarations`
-# fires once per rule in them — ~180 errors for `styles.css` alone — so staging
+# fires once per rule in them — ~180 errors for `guide.css` alone — so staging
 # one to change a single declaration blocks the commit outright. The rule is
 # about hand-written source readability and says nothing useful about minified
-# output that is about to be deleted.
+# legacy output. Migrating one of these into `src/` means bringing it up to the
+# design system in the same change, at which point it gets linted like any
+# other source file.
 #
 # `public/fonts/fonts.css` is deliberately NOT here: it is new, hand-written,
 # and must stay linted.
-#
-# Root-anchored on purpose: a bare `rules` would also swallow .agents/rules/.
-/styles.css
-/landing.css
-/chapters.css
-/responsive.css
-/skills-review/
-/rules/
-/skills/
-/full-guide/
+/legacy/