fix(ui): default the profileless client to Erudit only, not every variant

availableVariants fell back to all three variants when the player had no
stored preferences. A fresh offline native launch boots with no profile, so
New Game exposed the English game before the player opted in — contrary to the
backend's Erudit-only new-account default (docs/FUNCTIONAL.md). Fall back to
DEFAULT_VARIANTS (Erudit only) instead; all dictionaries stay bundled.

ui/src/lib/variants.test.ts

@@ -2,6 +2,7 @@ import { describe, it, expect } from 'vitest';
 
 import {
   ALL_VARIANTS,
+  DEFAULT_VARIANTS,
   availableVariants,
   supportsMultipleWordsToggle,
   multipleWordsForRequest,
@@ -16,9 +17,11 @@ describe('ALL_VARIANTS', () => {
 });
 
 describe('availableVariants', () => {
-  it('is ungated (all variants) for an empty or absent preference set', () => {
-    expect(availableVariants([])).toEqual(ALL_VARIANTS);
-    expect(availableVariants(undefined)).toEqual(ALL_VARIANTS);
+  it('falls back to the Erudit-only default for an empty or absent preference set', () => {
+    const fallback = ALL_VARIANTS.filter((v) => DEFAULT_VARIANTS.includes(v.id));
+    expect(fallback.map((v) => v.id)).toEqual(['erudit_ru']);
+    expect(availableVariants([])).toEqual(fallback);
+    expect(availableVariants(undefined)).toEqual(fallback);
   });
 
   it('offers only the preferred variants', () => {

ui/src/lib/variants.ts

@@ -62,13 +62,23 @@ export function usesStarBlank(v: Variant): boolean {
   return v === 'erudit_ru';
 }
 
-// availableVariants gates ALL_VARIANTS by the player's variant preferences (the set
-// they enabled in Settings). An empty or absent set is ungated (returns every variant)
-// — a safety fallback; a real profile always carries at least one preference.
+// 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.
+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.
 export function availableVariants(preferences: Variant[] | undefined): VariantOption[] {
   const prefs = preferences ?? [];
-  if (prefs.length === 0) return ALL_VARIANTS;
-  return ALL_VARIANTS.filter((v) => prefs.includes(v.id));
+  const effective = prefs.length === 0 ? DEFAULT_VARIANTS : prefs;
+  return ALL_VARIANTS.filter((v) => effective.includes(v.id));
 }
 
 // supportsMultipleWordsToggle reports whether the New Game "multiple words per turn" toggle