feat(ui): single-word rule indicators + auto-match select redesign

Surface the per-game "single word" rule to the client and refine the
random-opponent New Game screen.

- Wire: thread multiple_words_per_turn into the GameView and Invitation
  FlatBuffers tables (Go + TS regenerated), through pkg/wire builders and both
  the backend push-event and gateway REST paths.
- In-game indicators (single-word games only): a small 1 in the status bar's
  score-preview slot (yields to the live preview) and a centred "One word per
  turn" label in the history-drawer header. Standard games show neither.
- Invitation card gains a "One word per turn" line for single-word invitations.
- Auto-match redesign: variant plaques are mutually-exclusive selects (highlight
  on tap, no longer enqueue); a lone offered variant is pre-selected; a bottom
  "Start game" button (disabled until a variant is chosen) confirms. The rule
  toggle appears once a Russian variant is selected.
- Tests: e2e for the new auto flow and the in-game indicator (mock g3 is a
  single-word game); mock/data + fixtures carry the new field. Docs: UI_DESIGN.

ui/src/lib/codec.ts

@@ -238,6 +238,7 @@ function decodeGameView(g: fb.GameView): GameView {
     players: g.players(),
     toMove: g.toMove(),
     turnTimeoutSecs: g.turnTimeoutSecs(),
+    multipleWordsPerTurn: g.multipleWordsPerTurn(),
     moveCount: g.moveCount(),
     endReason: s(g.endReason()),
     lastActivityUnix: Number(g.lastActivityUnix()),
@@ -686,6 +687,7 @@ function decodeInvitationTable(i: fb.Invitation): Invitation {
     turnTimeoutSecs: i.turnTimeoutSecs(),
     hintsAllowed: i.hintsAllowed(),
     hintsPerPlayer: i.hintsPerPlayer(),
+    multipleWordsPerTurn: i.multipleWordsPerTurn(),
     dropoutTiles: s(i.dropoutTiles()),
     status: s(i.status()),
     gameId: s(i.gameId()),
@@ -721,6 +723,7 @@ function emptyGame(): GameView {
     players: 0,
     toMove: 0,
     turnTimeoutSecs: 0,
+    multipleWordsPerTurn: true,
     moveCount: 0,
     endReason: '',
     lastActivityUnix: 0,

ui/src/lib/gamedelta.test.ts

@@ -12,6 +12,7 @@ function gameView(moveCount: number, over = false): GameView {
     players: 2,
     toMove: 1,
     turnTimeoutSecs: 300,
+    multipleWordsPerTurn: true,
     moveCount,
     endReason: over ? 'standard' : '',
     lastActivityUnix: 0,

ui/src/lib/i18n/en.ts

@@ -69,6 +69,7 @@ export const en = {
   'game.dropGame': 'Drop game',
   'game.previewWords': '{words}: {n}',
   'game.previewIllegal': 'Not a legal move',
+  'game.oneWordRule': 'One word per turn',
   'game.chooseBlank': 'Choose a letter for the blank',
   'game.exchangeTitle': 'Select tiles to exchange',
   'game.exchangeConfirm': 'Exchange {n}',
@@ -233,6 +234,7 @@ export const en = {
   'new.moveTime': 'Move time',
   'new.hintsPerPlayer': 'Hints per player',
   'new.multipleWordsPerTurn': 'Multiple words per turn',
+  'new.start': 'Start game',
   'new.invited': 'Invitation sent.',
   'new.noFriends': 'Add friends first to invite them.',
 

ui/src/lib/i18n/ru.ts

@@ -70,6 +70,7 @@ export const ru: Record<MessageKey, string> = {
   'game.dropGame': 'Покинуть игру',
   'game.previewWords': '{words}: {n}',
   'game.previewIllegal': 'Недопустимый ход',
+  'game.oneWordRule': 'Одно слово за ход',
   'game.chooseBlank': 'Выберите букву для бланка',
   'game.exchangeTitle': 'Выберите фишки для обмена',
   'game.exchangeConfirm': 'Обменять {n}',
@@ -234,6 +235,7 @@ export const ru: Record<MessageKey, string> = {
   'new.moveTime': 'Время на ход',
   'new.hintsPerPlayer': 'Подсказок на игрока',
   'new.multipleWordsPerTurn': 'Несколько слов за ход',
+  'new.start': 'Начать игру',
   'new.invited': 'Приглашение отправлено.',
   'new.noFriends': 'Сначала добавьте друзей, чтобы пригласить их.',
 

ui/src/lib/lobbysort.test.ts

@@ -21,6 +21,7 @@ function game(id: string, status: GameView['status'], toMove: number, lastActivi
     players: 2,
     toMove,
     turnTimeoutSecs: 0,
+    multipleWordsPerTurn: true,
     moveCount: 0,
     endReason: '',
     lastActivityUnix,

ui/src/lib/mock/client.ts

@@ -142,7 +142,7 @@ export class MockGateway implements GatewayClient {
   }
 
   // --- lobby ---
-  async lobbyEnqueue(variant: Variant, _multipleWords: boolean): Promise<MatchResult> {
+  async lobbyEnqueue(variant: Variant, multipleWords: boolean): Promise<MatchResult> {
     // Simulate a 10s-style robot substitution, sped up: match found shortly.
     const id = crypto.randomUUID();
     const g: MockGame = {
@@ -154,6 +154,7 @@ export class MockGateway implements GatewayClient {
         players: 2,
         toMove: 0,
         turnTimeoutSecs: 86400,
+        multipleWordsPerTurn: multipleWords,
         moveCount: 0,
         endReason: '',
         lastActivityUnix: Math.floor(Date.now() / 1000),
@@ -442,6 +443,7 @@ export class MockGateway implements GatewayClient {
       turnTimeoutSecs: settings.turnTimeoutSecs,
       hintsAllowed: settings.hintsAllowed,
       hintsPerPlayer: settings.hintsPerPlayer,
+      multipleWordsPerTurn: settings.multipleWordsPerTurn,
       dropoutTiles: settings.dropoutTiles,
       status: 'pending',
       gameId: '',

ui/src/lib/mock/data.ts

@@ -61,6 +61,7 @@ export function mockInvitations(): Invitation[] {
       turnTimeoutSecs: 86400,
       hintsAllowed: true,
       hintsPerPlayer: 1,
+      multipleWordsPerTurn: true,
       dropoutTiles: 'remove',
       status: 'pending',
       gameId: '',
@@ -141,6 +142,7 @@ function activeGame(): MockGame {
       players: 2,
       toMove: 0,
       turnTimeoutSecs: 86400,
+      multipleWordsPerTurn: true,
       moveCount: G1_MOVES.length,
       endReason: '',
       lastActivityUnix: Math.floor(Date.now() / 1000) - 7200,
@@ -175,6 +177,7 @@ function finishedG2(): MockGame {
       players: 2,
       toMove: 0,
       turnTimeoutSecs: 86400,
+      multipleWordsPerTurn: true,
       moveCount: 2,
       endReason: 'normal',
       lastActivityUnix: Math.floor(Date.now() / 1000) - 86400,
@@ -210,6 +213,7 @@ function finishedG3(): MockGame {
       players: 2,
       toMove: 0,
       turnTimeoutSecs: 86400,
+      multipleWordsPerTurn: false,
       moveCount: 1,
       endReason: 'resignation',
       lastActivityUnix: Math.floor(Date.now() / 1000) - 172800,

ui/src/lib/model.ts

@@ -38,6 +38,8 @@ export interface GameView {
   players: number;
   toMove: number;
   turnTimeoutSecs: number;
+  /** true = standard Scrabble; false = the single-word rule (Russian games). */
+  multipleWordsPerTurn: boolean;
   moveCount: number;
   endReason: string;
   /** Lobby sort key: the current turn's start (active) or the finish time (finished), Unix seconds. */
@@ -177,6 +179,8 @@ export interface Invitation {
   turnTimeoutSecs: number;
   hintsAllowed: boolean;
   hintsPerPlayer: number;
+  /** true = standard Scrabble; false = the single-word rule (Russian games). */
+  multipleWordsPerTurn: boolean;
   dropoutTiles: string;
   status: string;
   gameId: string;

ui/src/lib/result.test.ts

@@ -20,6 +20,7 @@ function game(seats: Seat[], status = 'finished', toMove = 0): GameView {
     players: seats.length,
     toMove,
     turnTimeoutSecs: 0,
+    multipleWordsPerTurn: true,
     moveCount: 0,
     endReason: '',
     lastActivityUnix: 0,