Applied as-is. initLang and switchLang record a request counter before the first await and apply a pack only when that request is still the latest. Choosing the language already on screen cancels an in-flight load. A failed latest choice still saves the preference and leaves the previous UI.
Tests: node --test test/ui/lang.test.js test/ui/i18n.e2e.test.js test/i18n-packs.test.js test/i18n-server.test.js — 29 pass, 0 fail. The Chrome suite in test/ui/i18n.e2e.test.js skipped (SP_E2E unset).
