Stage 7 (wip): UI shell, libs, mock transport, screens (lobby->game), e2e smoke

- plain Svelte 5 + TS + Vite (no SvelteKit); CSS-token design system (Telegram-ready), hash router, IndexedDB session
- pure libs: domain model, premium/value maps ported from solver, board replay, placement state machine, i18n en/ru
- in-memory mock transport + seed data; pnpm start runs lobby->active game->board with no backend
- board: pointer-drag + tap placement, MakeMove (popup / 1s-hold commit), two-state zoom, blank chooser, exchange, hint, word-check, chat
- Playwright smoke (mock) green; svelte-check clean; mock bundle ~37 KB gzip

ui/src/lib/i18n/catalog.ts

@@ -0,0 +1,37 @@
+// Pure i18n catalog + lookup (no runes) so any module can import the types and
+// translate without depending on the reactive layer.
+
+import { en, type MessageKey } from './en';
+import { ru } from './ru';
+
+export type Locale = 'en' | 'ru';
+export type { MessageKey };
+
+export const catalogs: Record<Locale, Record<MessageKey, string>> = { en, ru };
+
+export function translate(
+  locale: Locale,
+  key: MessageKey,
+  params?: Record<string, string | number>,
+): string {
+  const dict = catalogs[locale] ?? en;
+  let s: string = dict[key] ?? en[key] ?? key;
+  if (params) {
+    for (const [k, v] of Object.entries(params)) {
+      s = s.replaceAll(`{${k}}`, String(v));
+    }
+  }
+  return s;
+}
+
+/** errorKey maps a gateway result/edge code to a message key, falling back to generic. */
+export function errorKey(code: string): MessageKey {
+  const key = `error.${code}` as MessageKey;
+  return key in en ? key : 'error.generic';
+}
+
+/** localeFrom picks a supported locale from a free-form hint (e.g. 'ru-RU' -> 'ru'). */
+export function localeFrom(hint: string | undefined | null, fallback: Locale = 'en'): Locale {
+  const l = (hint ?? '').slice(0, 2).toLowerCase();
+  return l === 'ru' ? 'ru' : l === 'en' ? 'en' : fallback;
+}