feat(variants): default a registered account to Erudit + Russian Scrabble

New Game opened on a single variant for everyone, which reads poorly on VK
where Russian Scrabble is the familiar game. A registered account now starts
with both Russian-alphabet games, so the picker offers a real choice with no
pre-selection.

A guest stays on Erudit alone and is invited to register for the rest: the
device-local guest has no profile at all, so the client-side fallback has to
keep matching the server. Registering promotes the set, but only while the
guest still carries the untouched guest default. Existing accounts are not
backfilled — the set they carry may be a deliberate choice.

The Telegram promo start-param becomes additive rather than a replacement,
with English Scrabble withheld from a Russian-speaking arrival; otherwise the
English campaign link would have taken Russian Scrabble away from every
account it onboarded.

ui/src/lib/i18n/en.ts

@@ -83,6 +83,11 @@ export const en = {
   'new.moveLimit': 'Move time: {n} h 00 min',
   'new.searchHint':
     'Finding an opponent can sometimes take a while. If you do not want to wait, close the app after starting the game and come back in a couple of minutes.',
+  // The guest's invitation to register, shown under the single variant a guest is offered. It is
+  // two keys because the first word is a link to the profile screen; the tail carries its own
+  // leading space, since Svelte trims literal whitespace at the edges of markup.
+  'new.guestVariantHintLink': 'Register',
+  'new.guestVariantHint': ' to play the Russian or English Scrabble.',
 
   // First-run coachmark hints (components/Coachmark.svelte). The leading emoji in each comment
   // names the UI element the bubble's tail points at.

ui/src/lib/i18n/ru.ts

@@ -84,6 +84,8 @@ export const ru: Record<MessageKey, string> = {
   'new.moveLimit': 'Время на ход: {n} ч. 00 мин.',
   'new.searchHint':
     'Иногда поиск соперника может занять некоторое время. Если не захотите ждать после начала игры, можете вернуться в приложение через несколько минут.',
+  'new.guestVariantHintLink': 'Зарегистрируйтесь',
+  'new.guestVariantHint': ', чтобы играть в русский или английский вариант Скрэббл.',
 
   // Подсказки первого запуска (components/Coachmark.svelte).
   'onboarding.lobbySettings': 'Друзья, настройки игры и профиля, обратная связь', // ⚙️

ui/src/lib/variants.test.ts

@@ -4,6 +4,7 @@ import {
   ALL_VARIANTS,
   DEFAULT_VARIANTS,
   availableVariants,
+  showRegisterHint,
   supportsMultipleWordsToggle,
   multipleWordsForRequest,
   usesStarBlank,
@@ -38,6 +39,18 @@ describe('availableVariants', () => {
   });
 });
 
+describe('showRegisterHint', () => {
+  it('invites only an online guest holding a single variant', () => {
+    expect(showRegisterHint(true, 1, false)).toBe(true);
+  });
+
+  it('stays hidden for a registered player, offline, or when several variants are offered', () => {
+    expect(showRegisterHint(false, 1, false)).toBe(false);
+    expect(showRegisterHint(true, 1, true)).toBe(false);
+    expect(showRegisterHint(true, 2, false)).toBe(false);
+  });
+});
+
 describe('supportsMultipleWordsToggle', () => {
   it('is true for Russian variants only', () => {
     expect(supportsMultipleWordsToggle('scrabble_ru')).toBe(true);

ui/src/lib/variants.ts

@@ -73,23 +73,32 @@ export function usesStarBlank(v: Variant): boolean {
 
 // DEFAULT_VARIANTS is the variant set a player sees before any preference is stored — a fresh
 // or offline native client whose profile has not been synced yet (the device-local guest boots
-// with no profile at all). It mirrors the backend's new-account default (the account service
-// seeds Erudit only), so the local guest and a later synced account agree on what is enabled.
-// Every dictionary is still bundled; the other variants are simply off until the player turns
-// them on in Settings.
+// with no profile at all). Such a client is a guest, so it mirrors the backend's *guest* set
+// (account.GuestVariantPreferences, Erudit alone) rather than the wider set a registered account
+// is created with. Every dictionary is still bundled; the other variants are simply off until
+// the player registers and turns them on in Settings.
 export const DEFAULT_VARIANTS: Variant[] = ['erudit_ru'];
 
 // availableVariants gates ALL_VARIANTS by the player's variant preferences (the set they
 // enabled in Settings). An empty or absent set falls back to DEFAULT_VARIANTS rather than every
 // variant: a real profile always carries at least one preference, and a profileless client (a
-// fresh offline native launch) must match the server's Erudit-only default instead of exposing
-// the English game before the player opts in.
+// fresh offline native launch) must match the server's guest default instead of exposing
+// the other games before the player opts in.
 export function availableVariants(preferences: Variant[] | undefined): VariantOption[] {
   const prefs = preferences ?? [];
   const effective = prefs.length === 0 ? DEFAULT_VARIANTS : prefs;
   return ALL_VARIANTS.filter((v) => effective.includes(v.id));
 }
 
+// showRegisterHint reports whether New Game invites the player to register in order to unlock the
+// other games, given whether they are a guest (isGuest), how many variants they are offered
+// (offered) and whether the app is in offline mode (offline). It is the guest's case alone: a
+// guest is created with Erudit only, while registering widens the account to both Russian-alphabet
+// games. Offline it is suppressed — registration needs the network, so the link would be dead.
+export function showRegisterHint(isGuest: boolean, offered: number, offline: boolean): boolean {
+  return isGuest && !offline && offered === 1;
+}
+
 // supportsMultipleWordsToggle reports whether the New Game "multiple words per turn" toggle
 // applies to a variant. Only Russian games choose the rule; English is always standard, so
 // its toggle is not shown.

ui/src/screens/NewGame.svelte

@@ -22,6 +22,7 @@
   import type { AccountRef, GameView, Variant } from '../lib/model';
   import {
     availableVariants,
+    showRegisterHint,
     VARIANT_FLAG,
     VARIANT_RULES,
     supportsMultipleWordsToggle,
@@ -395,6 +396,13 @@
             </button>
           {/each}
         </div>
+        <!-- A guest is offered Erudit alone; registering widens the account to both Russian games
+             (and Settings then offers English), so point them at the profile screen. -->
+        {#if showRegisterHint(guest, variants.length, offlineMode.active)}
+          <p class="guesthint">
+            <button class="hintlink" onclick={() => navigate('/profile')}>{t('new.guestVariantHintLink')}</button>{t('new.guestVariantHint')}
+          </p>
+        {/if}
         {#if variants.some((v) => supportsMultipleWordsToggle(v.id))}
           <label class="toggle">
             <span>{t('new.multipleWordsPerTurn')}</span>
@@ -771,6 +779,24 @@
     font-size: 0.85rem;
     line-height: 1.4;
   }
+  /* The guest's register invitation: a muted line opening with an inline link-styled button
+     that routes to the profile screen (mirrors Profile's .linklike). */
+  .guesthint {
+    margin: 0;
+    text-align: center;
+    color: var(--text-muted);
+    font-size: 0.85rem;
+    line-height: 1.4;
+  }
+  .hintlink {
+    background: none;
+    border: none;
+    padding: 0;
+    color: var(--accent);
+    font: inherit;
+    text-decoration: underline;
+    cursor: pointer;
+  }
   /* The offline-blocker reason (a missing dictionary, or the online segment needing a connection). */
   .dictnote {
     margin: 0;