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/board.ts

@@ -0,0 +1,45 @@
+// Pure board reconstruction. The wire carries no board (StateView is summary + rack
+// only), so the live grid is rebuilt by replaying the decoded move journal — exactly
+// the dictionary-independent history invariant (ARCHITECTURE §9.1): apply each play's
+// placed tiles onto an empty grid.
+
+import type { MoveRecord, Tile } from './model';
+import { BOARD_SIZE } from './premiums';
+
+export interface BoardCell {
+  letter: string;
+  blank: boolean;
+}
+
+export type Board = (BoardCell | null)[][];
+
+export function emptyBoard(): Board {
+  return Array.from({ length: BOARD_SIZE }, () =>
+    Array.from({ length: BOARD_SIZE }, () => null as BoardCell | null),
+  );
+}
+
+function inBounds(r: number, c: number): boolean {
+  return r >= 0 && r < BOARD_SIZE && c >= 0 && c < BOARD_SIZE;
+}
+
+/** replay folds every play move's tiles onto an empty board (pass/exchange/resign
+ * change no squares). */
+export function replay(moves: MoveRecord[]): Board {
+  const b = emptyBoard();
+  for (const m of moves) {
+    if (m.action !== 'play') continue;
+    for (const t of m.tiles) {
+      if (inBounds(t.row, t.col)) b[t.row][t.col] = { letter: t.letter, blank: t.blank };
+    }
+  }
+  return b;
+}
+
+/** lastPlayTiles returns the tiles of the most recent play (for highlighting). */
+export function lastPlayTiles(moves: MoveRecord[]): Tile[] {
+  for (let i = moves.length - 1; i >= 0; i--) {
+    if (moves[i].action === 'play') return moves[i].tiles;
+  }
+  return [];
+}