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/components/Toast.svelte

@@ -0,0 +1,29 @@
+<script lang="ts">
+  import { app } from '../lib/app.svelte';
+</script>
+
+{#if app.toast}
+  <div class="toast {app.toast.kind}" role="status" aria-live="polite">{app.toast.text}</div>
+{/if}
+
+<style>
+  .toast {
+    position: fixed;
+    left: 50%;
+    bottom: 24px;
+    transform: translateX(-50%);
+    max-width: min(92vw, 420px);
+    padding: 10px 16px;
+    border-radius: var(--radius);
+    background: var(--surface);
+    color: var(--text);
+    border: 1px solid var(--border);
+    box-shadow: var(--shadow);
+    z-index: 50;
+    text-align: center;
+  }
+  .error {
+    border-color: var(--danger);
+    color: var(--danger);
+  }
+</style>