feat(i18n): locale-expansion tooling — add-locale orchestrator, aliases, translation-ratio gate; retire duplicate 'in' locale (#12496)

Locale aliases (uk, fil/tl, zh-hant, legacy in→id) with fixed browser/CLI/cookie detection; config/i18n.json shipped in the npm package; duplicate 'in' locale retired (42 honest locales); real-translation ratio gate with ratchet baseline (advisory); add-locale orchestrator + shared libs (batched translation backend, config-generated language bars, run-translation --adopt/--targets-only, scaffold helpers); tests derive the locale count from config with surface parity guards; docs and every public locale-count claim aligned.

.github/workflows/ci.yml

@@ -502,6 +502,11 @@ jobs:
           cache: npm
       - uses: ./.github/actions/npm-ci-retry
       - run: node scripts/i18n/check-ui-keys-coverage.mjs --threshold=65
+      # Real-translation ratchet: a leaf copied verbatim from en.json passes key
+      # parity above but is still English to the user (es shipped 55% English).
+      # Advisory in PR-0; flipped to blocking once the backlog is retranslated (PR-4).
+      - name: i18n real-translation ratio (advisory)
+        run: node scripts/i18n/check-translation-ratio.mjs --warn
       # #8463: a rewritten English value used to leave its 39 translations behind
       # silently (googleOAuthWarning shipped wrong copy in 39 locales for months).
       # Key parity above cannot see it — a stale translation counts as covered.