Add a string or a locale

Every user-facing string is a key in packages/i18n/messages/<locale>.json (en.json only today). .claude/rules/i18n.md has the rules.

A string

1. Pick the namespace (top-level key) the surface uses: auth, settings, shorts, director, email, errors, … and put the key next to its siblings. Reuse common.* for shared words (Save, Cancel).
2. Add it to every catalog, at the same path, in the same change. Write real translations; if you can't, say so in the pull request rather than copying English.
3. ICU for anything variable: {name}, {count, plural, one {# item} other {# items}}. Never concatenate translated fragments. Arguments aren't type-checked (the catalog is imported as JSON), so pass exactly the ones the message names.
4. Use it: useTranslations("<ns>") (web client), getTranslations from next-intl/server (web server components), the translator in apps/notifications for emails. Dates, numbers and money through useFormatter() / getFormatter().
5. Keys the code checks for: an error code needs errors.<CODE>; an event workspace.audit.events.<domain>.<fact>.v<N> (nested, like auth.signed_up.v1).

A locale

1. Copy packages/i18n/messages/en.json to <code>.json and translate it.
2. Add the code to locales and to catalogs in packages/i18n/src/index.ts (the satisfies clause makes a missing key a type error).
3. Right-to-left: add it to RTL in apps/web/src/app/layout.tsx.
4. The profile settings' language list reads locales, so it picks it up. With more than one language, the header's language switcher (removed while English was the only one) and the saved-language half of PreferenceSync come back.

Done when

• bun run check-types passes (web keys are checked against English).
• bun run --filter @repo/i18n test passes (every catalog complete; codes, events, categories and scopes all have their keys).
• bun run --filter @repo/email test if an email changed.
• The i18n-checker agent reports nothing blocking.