The salvaged commit added the key to web/src/i18n/types.ts and en.ts
only; the 15 web locales typed as full Translations (fr/de/es/it/pt/
ru/tr/uk/ko/ja/zh/zh-hant/af/ga/hu) then failed 'tsc -b' (the real
build path) with TS2741. web/ar.ts uses defineLocale and falls back
to en, so it needs nothing. Follow-up for salvaged PR #98716.