fix: a bot outage no longer freezes the board on "thinking…"

requestBotMove retried forever on failure and did nothing at all when the engine
answered without a move, so a Stockfish hiccup left the player watching the
thinking indicator with no way to continue.

Now: four attempts with exponential backoff, then a dialog offering to end the
game. Also guards against gameState having been torn down mid-request.

The engine itself is healthy — verified live: GET /api/chess/bots returns the
seven bots the client expects, and POST /api/chess/move answers the start
position with d2d4 at depth 3. api/bots.php's paths are correct.

Arabic and English strings added for the new message.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

public/js/core/i18n.js

@@ -43,6 +43,7 @@ const strings = {
     'game.you_lose': 'خسرت',
     'game.draw_result': 'تعادل',
     'game.thinking': 'يفكر...',
+    'game.bot_unavailable': 'الخصم الآلي لا يستجيب. هل تريد إنهاء هذه المباراة؟',
     'game.your_turn': 'دورك',
     'game.opponent_turn': 'دور الخصم',
     'rank.title': 'الترتيب',
@@ -757,6 +758,7 @@ const strings = {
     'game.you_lose': 'You Lose',
     'game.draw_result': 'Draw',
     'game.thinking': 'Thinking...',
+    'game.bot_unavailable': 'The computer opponent is not responding. End this game?',
     'game.your_turn': 'Your Turn',
     'game.opponent_turn': "Opponent's Turn",
     'rank.title': 'Rankings',

public/js/modules/chess/scenes/game.js

@@ -448,10 +448,11 @@ function executeMove(el, from, to, promotion) {
   }
 }
 
-async function requestBotMove(el) {
+async function requestBotMove(el, attempt = 0) {
+  if (!gameState || gameState.gameOver) return;
   gameState.botThinking = true;
   const thinkingEl = el.querySelector('#bot-thinking');
-  thinkingEl.style.display = 'block';
+  if (thinkingEl) thinkingEl.style.display = 'block';
 
   try {
     const data = await net.post('bots.php', {
@@ -460,9 +461,17 @@ async function requestBotMove(el) {
       bot_id: gameState.botId
     });
 
-    thinkingEl.style.display = 'none';
+    if (!gameState) return;
+    if (thinkingEl) thinkingEl.style.display = 'none';
     gameState.botThinking = false;
 
+    // An engine that answers but cannot produce a move leaves the board frozen
+    // on "thinking…" forever unless we say something.
+    if (!data.best_move && !gameState.gameOver) {
+      botUnavailable(el);
+      return;
+    }
+
     if (data.best_move && !gameState.gameOver) {
       const from = data.best_move.substring(0, 2);
       const to = data.best_move.substring(2, 4);
@@ -505,12 +514,38 @@ async function requestBotMove(el) {
       }
     }
   } catch (e) {
-    thinkingEl.style.display = 'none';
+    if (!gameState) return;
+    if (thinkingEl) thinkingEl.style.display = 'none';
     gameState.botThinking = false;
-    setTimeout(() => requestBotMove(el), 2000);
+
+    // This used to retry forever, so an engine outage left the player staring at
+    // "thinking…" with no way forward. Back off, then give up gracefully.
+    if (attempt < 4) {
+      const delay = 1000 * Math.pow(2, attempt);
+      setTimeout(() => requestBotMove(el, attempt + 1), delay);
+    } else {
+      botUnavailable(el);
+    }
   }
 }
 
+/** The engine is not answering. Tell the player and let them leave. */
+function botUnavailable(el) {
+  if (!gameState || gameState.gameOver) return;
+  gameState.botThinking = false;
+  const thinkingEl = el.querySelector('#bot-thinking');
+  if (thinkingEl) thinkingEl.style.display = 'none';
+  mpLogFront('bot_unavailable', { botId: gameState.botId });
+  modal.confirm(t('game.bot_unavailable') || 'The computer opponent is not responding. End this game?', {
+    title: t('game.bot') || 'Bot',
+    icon: '🤖',
+    confirmText: t('common.confirm') || 'OK',
+    cancelText: t('common.cancel') || 'Cancel'
+  }).then(ok => {
+    if (ok) endGame('draw', 'aborted');
+  });
+}
+
 function updateCapturedDisplay(el) {
   const pieceSymbols = { p: '♟', n: '♞', b: '♝', r: '♜', q: '♛', k: '♚' };
   const pieceOrder = ['q', 'r', 'b', 'n', 'p'];