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>

package.json

@@ -12,7 +12,6 @@
     "verify": "node scripts/verify.mjs && node scripts/audit-ui.mjs && node .agents/scripts/check-tokens.mjs",
     "gate": "./.agents/scripts/gate.sh",
     "snapshot": "node .agents/scripts/snapshot-route.mjs",
-    "serve": "python3 -m http.server 4173",
     "prepare": "husky"
   },
   "devDependencies": {