feat(chess): add dismiss/clear-all for finished games in lobby

Persist dismissed game IDs locally (SharedPreferences on Android,
java.util.prefs on Desktop) so completed games can be permanently
hidden from the chess lobby. Adds per-game dismiss button and
"Clear all" action when 2+ finished games exist.

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

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/chess/ChessScreen.kt

@@ -53,6 +53,7 @@ import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.collectAsState
@@ -339,6 +340,8 @@ fun ChessScreen(
                 onOpenOwnChallenge = { viewModel.openOwnChallenge(it) },
                 onWatchGame = { viewModel.loadGameAsSpectator(it) },
                 onSelectGame = { viewModel.selectGame(it) },
+                onDismissGame = { viewModel.dismissCompletedGame(it) },
+                onDismissAllGames = { viewModel.dismissAllCompletedGames() },
                 listState = listState,
             )
         }
@@ -372,6 +375,8 @@ private fun ChessLobby(
     onOpenOwnChallenge: (ChessChallenge) -> Unit,
     onWatchGame: (String) -> Unit,
     onSelectGame: (String) -> Unit,
+    onDismissGame: (String) -> Unit,
+    onDismissAllGames: () -> Unit,
     listState: LazyListState = rememberLazyListState(),
 ) {
     val hasContent =
@@ -581,12 +586,22 @@ private fun ChessLobby(
         if (completedGames.isNotEmpty()) {
             item {
                 Spacer(Modifier.height(16.dp))
-                Text(
-                    "Recent Games",
-                    style = MaterialTheme.typography.titleMedium,
-                    fontWeight = FontWeight.Bold,
-                    modifier = Modifier.padding(vertical = 8.dp),
-                )
+                Row(
+                    modifier = Modifier.fillMaxWidth().padding(vertical = 8.dp),
+                    horizontalArrangement = Arrangement.SpaceBetween,
+                    verticalAlignment = Alignment.CenterVertically,
+                ) {
+                    Text(
+                        "Recent Games",
+                        style = MaterialTheme.typography.titleMedium,
+                        fontWeight = FontWeight.Bold,
+                    )
+                    if (completedGames.size >= 2) {
+                        TextButton(onClick = onDismissAllGames) {
+                            Text("Clear all")
+                        }
+                    }
+                }
             }
 
             items(
@@ -603,6 +618,7 @@ private fun ChessLobby(
                     isDraw = game.isDraw,
                     moveCount = game.moveCount,
                     onClick = { onSelectGame(game.gameId) },
+                    onDismiss = { onDismissGame(game.gameId) },
                     avatar = {
                         UserAvatar(
                             userHex = opponentPubkey,

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/chess/DesktopChessViewModelNew.kt

@@ -22,6 +22,7 @@ package com.vitorpamplona.amethyst.desktop.chess
 
 import com.vitorpamplona.amethyst.commons.chess.ChessBroadcastStatus
 import com.vitorpamplona.amethyst.commons.chess.ChessChallenge
+import com.vitorpamplona.amethyst.commons.chess.ChessDismissedGamesStorage
 import com.vitorpamplona.amethyst.commons.chess.ChessLobbyLogic
 import com.vitorpamplona.amethyst.commons.chess.ChessPollingDefaults
 import com.vitorpamplona.amethyst.commons.chess.ChessSyncStatus
@@ -59,6 +60,7 @@ class DesktopChessViewModelNew(
     private val publisher = DesktopChessPublisher(account, relayManager)
     private val fetcher = DesktopRelayFetcher(relayManager, account.pubKeyHex)
     private val metadataProvider = DesktopMetadataProvider(userMetadataCache)
+    private val dismissedStorage = ChessDismissedGamesStorage.create()
 
     // Shared business logic (creates its own ChessLobbyState internally)
     private val logic =
@@ -69,6 +71,7 @@ class DesktopChessViewModelNew(
             metadataProvider = metadataProvider,
             scope = scope,
             pollingConfig = ChessPollingDefaults.desktop,
+            dismissedStorage = dismissedStorage,
         )
 
     // ============================================
@@ -164,6 +167,10 @@ class DesktopChessViewModelNew(
 
     fun dismissGame(gameId: String) = logic.dismissGame(gameId)
 
+    fun dismissCompletedGame(gameId: String) = logic.dismissCompletedGame(gameId)
+
+    fun dismissAllCompletedGames() = logic.dismissAllCompletedGames()
+
     // ============================================
     // Spectator operations
     // ============================================