feat(ui): explicit offline state inside an online game (+ offline word check)

When an online game loses the connection the game screen now says so and freezes
instead of silently greying out: a "connection lost" banner appears and the rack,
the move controls, the add-friend/block controls and the chat/dictionary entry all
disable (a started move stays a draft, committed by the player on reconnect). It is
driven off the net-state machine (netState.offline), so it also covers the
Telegram/VK mini-apps, where a lost connection was previously mute in-game.

If the player is already in the dictionary when the drop happens, the word check
falls back to the game's pinned on-device dictionary (exact when that dawg is
cached; "unavailable offline" otherwise) and the network-only complaint + external
look-up hide. Chat, when already open, keeps its existing read-only degrade
(send/nudge disable). New pure helper localWordCheck is unit-tested; the in-game
gating gets an e2e.

ui/src/game/Game.svelte

@@ -15,6 +15,7 @@
   import { app, handleError, showToast, markChatRead, seedChatUnread } from '../lib/app.svelte';
   import { connection } from '../lib/connection.svelte';
   import { offlineMode } from '../lib/offline.svelte';
+  import { netState } from '../lib/netstate.svelte';
   import { maybeShowInterstitial } from '../lib/ads';
   import { GatewayError } from '../lib/client';
   import { t, type MessageKey } from '../lib/i18n/index.svelte';
@@ -63,6 +64,10 @@
   // disabled while disconnected or in offline mode (which also stops the "something went wrong"
   // toasts a blocked call would otherwise raise).
   const netReady = $derived(isLocalGameId(id) || (connection.online && !offlineMode.active));
+  // offlineInGame marks an online game that has lost the connection (confirmed offline, on any
+  // platform including Telegram/VK): the play area shows an explicit "connection lost" banner and
+  // the tray/actions freeze. It follows netState (not offlineMode, which is inert in the mini-apps).
+  const offlineInGame = $derived(!isLocalGameId(id) && netState.offline);
   // Unsubscribes from a local game's robot-reply events (offline only; null for a network game).
   let localUnsub: (() => void) | null = null;
 
@@ -1463,6 +1468,7 @@
     // a local (offline) game, whose seats are account-less: vs_ai, and hotseat's synthetic seat ids.
     if (view?.game.vsAi || isLocalGameId(id)) return false;
     return (
+      netReady &&
       !!s.accountId &&
       !app.profile?.isGuest &&
       s.accountId !== app.session?.userId &&
@@ -1476,7 +1482,7 @@
   // An already-blocked opponent hides it (both controls go, and the name is struck).
   function canBlock(s: { accountId: string; seat: number }): boolean {
     if (view?.game.vsAi || isLocalGameId(id)) return false;
-    return !!s.accountId && !app.profile?.isGuest && s.accountId !== app.session?.userId && !seatBlocked(s);
+    return netReady && !!s.accountId && !app.profile?.isGuest && s.accountId !== app.session?.userId && !seatBlocked(s);
   }
 </script>
 
@@ -1490,6 +1496,9 @@
   selfInset={landscape}
 >
   {#if view}
+    {#if offlineInGame}
+      <div class="offline-banner" role="status">{t('game.offlineBanner')}</div>
+    {/if}
     {#if landscape}
       <div class="game-land">
         <div class="leftpane">
@@ -1607,7 +1616,7 @@
            — so drop the entry only when a local game is finished; an active local game keeps it for
            the Dictionary. An online game always keeps it (chat outlives the game). -->
       {#if !(gameOver && (view.game.vsAi || view.game.hotseat))}
-        <button class="hicon" onclick={() => navigate(`/game/${id}/chat`)} aria-label={t('game.chat')}>
+        <button class="hicon" disabled={!netReady} onclick={() => navigate(`/game/${id}/chat`)} aria-label={t('game.chat')}>
           {#key chatBlink}<span class="chat-ico" class:blink={chatBlink > 0 && !app.reduceMotion}>💬</span>{/key}
         </button>
       {/if}
@@ -1694,6 +1703,7 @@
           draggingId={reorderDragId}
           dropIndex={reorderTo}
           confirm={!gameOver && placement.pending.length > 0 && !recallOverRack ? confirmBtn : undefined}
+          frozen={!netReady}
           ondown={onRackDown}
         />
       {/if}
@@ -2178,6 +2188,17 @@
     color: var(--text-muted);
     padding: 40px;
   }
+  /* An online game that lost the connection: a slim, non-blocking strip at the top of the play area.
+     A solid token background (not color-mix) keeps it visible on the old-WebView floor. */
+  .offline-banner {
+    padding: 7px var(--pad);
+    text-align: center;
+    font-size: 0.85rem;
+    line-height: 1.25;
+    color: var(--text);
+    background: var(--surface-2);
+    border-bottom: 1px solid var(--border);
+  }
   .ghost {
     position: fixed;
     width: 40px;