fix: prevent double-fetch and stop re-polling finished chess games

- Mark recentlyLoadedGames timestamp eagerly in refreshGame (before
  async fetch) to prevent concurrent fetches for the same game
- Clear focused game in removeGameId when the removed game matches,
  so finished games stop being re-polled

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/chess/ChessEventPolling.kt

@@ -161,6 +161,10 @@ class ChessPollingDelegate(
      */
     fun removeGameId(gameId: String) {
         activeGameIdsFlow.value = activeGameIdsFlow.value - gameId
+        // If this was the focused game, clear focus to stop re-polling a finished game
+        if (_focusedGameId.value == gameId) {
+            _focusedGameId.value = null
+        }
     }
 
     /**

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/chess/ChessLobbyLogic.kt

@@ -677,6 +677,8 @@ class ChessLobbyLogic(
             Log.d("chessdebug", "[Lobby] refreshGame: SKIPPED game ${startEventId.take(8)} - loaded ${TimeUtils.now() - lastLoaded}s ago")
             return
         }
+        // Mark immediately to prevent concurrent fetches for the same game
+        recentlyLoadedGames[startEventId] = TimeUtils.now()
 
         Log.d("chessdebug", "[Lobby] refreshGame: fetching game ${startEventId.take(8)} from relays")
         val events = fetcher.fetchGameEvents(startEventId)