feat(offline): offline lobby lists + creates local vs_ai games

In offline mode the lobby now shows only the device-local games and its
New-vs-AI entry creates one through the in-browser engine — the visible
payoff of the offline mode.

- LocalSource.list() reconstructs a lobby GameView per stored local game by
  replay, exposed through the lazy gamesource proxy; unit-tested via an
  in-memory store.
- Lobby.load() branches on offlineMode: lists local games and skips every
  gateway call (no online games/invitations/incoming); the Stats tab is
  disabled offline.
- NewGame offline: find() creates a device-local vs_ai game via
  LocalSource.create using the profile's advertised dict version + a local
  seed; the friends flow and the random-opponent option are hidden, and the
  variant picker / Start are enabled offline (were gated on connection).
- id.ts: newLocalGameId + randomSeed (tested).

Docs: ARCHITECTURE + FUNCTIONAL(+ru) offline-mode section.

Deferred to fast-follow: the Settings Friends/Profile/Feedback affordance
gating, the flip-to-offline readiness wait, the offline mock e2e (needs
mock-dawg support), and the local-hint UI. The offline flow is verified on
the test contour — the mock e2e cannot enter offline mode (the toggle is
gated to an installed PWA).

ui/src/screens/Lobby.svelte

@@ -13,7 +13,8 @@
   import { badgeKind } from '../lib/unread';
   import { getLobby, setLobby } from '../lib/lobbycache';
   import { preloadGames } from '../lib/preload';
-  import { kickDictPreload } from '../lib/offline.svelte';
+  import { kickDictPreload, offlineMode } from '../lib/offline.svelte';
+  import { localSource } from '../lib/gamesource';
   import { gamePhase, groupGames, orderedSeats, scoreStanding, shouldBlink, type LobbyPhase } from '../lib/lobbysort';
   import type { AccountRef, GameView, Invitation } from '../lib/model';
   import { VARIANT_FLAG, VARIANT_RULES } from '../lib/variants';
@@ -34,6 +35,19 @@
   const settingsBadge = $derived(app.notifications + (app.feedbackReplyUnread ? 1 : 0));
 
   async function load() {
+    // Deliberate offline mode: never touch the network. The lobby shows only the device-local
+    // vs_ai games (reconstructed from the store) plus the New-vs-AI entry; there are no online
+    // games, invitations or incoming requests to fetch.
+    if (offlineMode.active) {
+      games = await localSource.list();
+      invitations = [];
+      incoming = [];
+      atGameLimit = false;
+      app.notifications = 0;
+      setLobby({ games, invitations, incoming, atGameLimit });
+      app.lobbyReady = true;
+      return;
+    }
     try {
       const list = await gateway.gamesList();
       games = list.games;
@@ -341,7 +355,7 @@
       <button class="tab" disabled={atGameLimit} onclick={() => navigate('/new')}>
         <span class="sq" data-coach="lobby-new">🎲</span><span class="lbl">{t('lobby.new')}</span>
       </button>
-      <button class="tab" onclick={() => navigate('/stats')}>
+      <button class="tab" disabled={offlineMode.active} onclick={() => navigate('/stats')}>
         <span class="sq" data-coach="lobby-stats">✏️</span><span class="lbl">{t('lobby.stats')}</span>
       </button>
       <button class="tab" onclick={() => navigate('/settings')}>

ui/src/screens/NewGame.svelte

@@ -4,6 +4,9 @@
   import { gateway } from '../lib/gateway';
   import { app, handleError, showToast } from '../lib/app.svelte';
   import { connection } from '../lib/connection.svelte';
+  import { offlineMode } from '../lib/offline.svelte';
+  import { localSource } from '../lib/gamesource';
+  import { newLocalGameId, randomSeed } from '../lib/localgame/id';
   import { navigate } from '../lib/router.svelte';
   import { t, type MessageKey } from '../lib/i18n/index.svelte';
   import type { AccountRef, Variant } from '../lib/model';
@@ -54,6 +57,30 @@
     if (starting) return;
     starting = true;
     try {
+      // Offline mode: create a device-local vs_ai game instead of enqueuing on the backend. The
+      // dictionary version comes from the profile (advertised for exactly this), and the bag is
+      // seeded locally; the same game screen then drives it through the local source.
+      if (offlineMode.active) {
+        const version = app.profile?.dictVersions?.[v];
+        if (!version) {
+          handleError(new Error('dict_unavailable'));
+          return;
+        }
+        const id = newLocalGameId();
+        await localSource.create({
+          id,
+          variant: v,
+          dictVersion: version,
+          seed: randomSeed(),
+          multipleWords: multipleWordsForRequest(v, multipleWords),
+          seats: [
+            { kind: 'human', name: app.profile?.displayName ?? 'You' },
+            { kind: 'robot', name: 'Robot' },
+          ],
+        });
+        navigate(`/game/${id}`);
+        return;
+      }
       const r = await gateway.lobbyEnqueue(v, multipleWordsForRequest(v, multipleWords), opponent === 'ai');
       if (r.game) navigate(`/game/${r.game.id}`);
     } catch (e) {
@@ -117,7 +144,9 @@
 
 <Screen title={t('new.title')} back="/">
   <div class="page">
-      {#if !guest}
+      <!-- Offline mode offers only a local vs_ai game: the friends flow needs the network, so the
+           auto/friends selector is hidden and the auto (vs_ai) flow shows on its own. -->
+      {#if !guest && !offlineMode.active}
         <div class="seg modes">
           <button class="opt" class:active={mode === 'auto'} onclick={() => (mode = 'auto')}>{t('new.auto')}</button>
           <button class="opt" class:active={mode === 'friends'} onclick={() => (mode = 'friends')}>{t('new.withFriends')}</button>
@@ -125,17 +154,19 @@
       {/if}
 
       {#if mode === 'auto'}
-        <div class="seg modes">
-          <button class="opt" class:active={opponent === 'ai'} onclick={() => (opponent = 'ai')}>🤖 {t('new.opponentAI')}</button>
-          <button class="opt" class:active={opponent === 'random'} onclick={() => (opponent = 'random')}>👤 {t('new.opponentRandom')}</button>
-        </div>
+        {#if !offlineMode.active}
+          <div class="seg modes">
+            <button class="opt" class:active={opponent === 'ai'} onclick={() => (opponent = 'ai')}>🤖 {t('new.opponentAI')}</button>
+            <button class="opt" class:active={opponent === 'random'} onclick={() => (opponent = 'random')}>👤 {t('new.opponentRandom')}</button>
+          </div>
+        {/if}
         <div class="variants">
           {#each variants as v (v.id)}
             <button
               class="variant"
               class:selected={selectedAuto === v.id}
               onclick={() => (selectedAuto = v.id)}
-              disabled={!connection.online}
+              disabled={!connection.online && !offlineMode.active}
             >
               <span class="vmain">
                 <span class="vname">{t(v.label)}</span>
@@ -160,7 +191,7 @@
         {#if opponent === 'random'}<p class="searchhint">{t('new.searchHint')}</p>{/if}
         <button
           class="invite"
-          disabled={!selectedAuto || !connection.online || starting}
+          disabled={!selectedAuto || (!connection.online && !offlineMode.active) || starting}
           onclick={() => selectedAuto && find(selectedAuto)}
         >{t('new.start')}</button>
       {:else if friends.length === 0}