fix: stop leaking a task number into site copy, ignore legacy sources

Two unrelated cleanups from the 14-17 wave.

The review desk footer told visitors to mirror entries into catalog.js
'until task 16 rewires the page to read the collection'. Introduced by
b484302 (task 06), it shipped in the built HTML. The mirroring advice is
still correct -- verify.mjs:24,52,54 confirm the desk reads catalog.js --
so only the internal task reference is dropped.

.prettierignore now covers the legacy sources. They have very long lines,
so lint-staged re-wraps them wholesale as soon as an agent stages one:
task 15 added four lines to app.js and produced an 829-line diff. Paths
are root-anchored so a bare 'rules' does not swallow .agents/rules/.

.agents/snapshots/skills-review.txt

@@ -45,7 +45,7 @@ submitted-skills/
 src/content/reviews/{new-id}.md
 (and mirror it into
 skills-review/catalog.js
-until task 16 rewires the page to read the collection), then run
+which the desk still reads), then run
 node scripts/build-skill-review.mjs
 . Votes call a separate service — see
 vote-service/