An audit found the client already i18n-first: one hard-coded UI string
(the battle-scene aria-label, now keyed) and en/ru already share an
identical 692-key set.
- Persist the locale: i18n.setLocale writes localStorage (galaxy-locale)
and the store boots from stored > browser detection > default, so a
language switch survives reloads.
- tests/i18n-completeness.test.ts: en/ru key-set parity, non-empty
values, and locale persistence.
- Docs: ui/docs/i18n.md; mark F3 done in ui/PLAN-finalize.md.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Ilia Denisov