feat(chess): exit spectator mode with Leave Game button

Adds ability to leave a spectated game on both Android and Desktop:
- Added stopSpectating() to ChessLobbyLogic (removes from state + stops polling)
- Both ViewModels now delegate to logic.stopSpectating() instead of bypassing it
- LiveChessGameScreen accepts onLeaveSpectating callback shown in spectator info area
- Android: Leave Game button pops back stack and stops spectating
- Desktop: Leave Game button clears selectedGameId (returns to lobby) and stops spectating

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

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chess/ChessGameScreen.kt

@@ -350,6 +350,15 @@ fun ChessGameScreen(
                     onResign = { chessViewModel.resign(gameId) },
                     isSpectatorOverride = isSpectating,
                     onGameEndDismiss = { chessViewModel.dismissGame(gameId) },
+                    onLeaveSpectating =
+                        if (isSpectating) {
+                            {
+                                chessViewModel.stopSpectating(gameId)
+                                nav.popBack()
+                            }
+                        } else {
+                            null
+                        },
                     whiteName = whiteDisplayName,
                     whiteHex = whitePubkey,
                     whiteAvatarUrl = whiteAvatarUrl,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chess/ChessViewModelNew.kt

@@ -176,7 +176,7 @@ class ChessViewModelNew(
 
     fun loadGameAsSpectator(gameId: String) = logic.loadGameAsSpectator(gameId)
 
-    fun stopSpectating(gameId: String) = logic.state.removeSpectatingGame(gameId)
+    fun stopSpectating(gameId: String) = logic.stopSpectating(gameId)
 
     // ============================================
     // Utility

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

@@ -505,6 +505,11 @@ class ChessLobbyLogic(
     // Spectator mode
     // ========================================
 
+    fun stopSpectating(gameId: String) {
+        state.removeSpectatingGame(gameId)
+        pollingDelegate.removeGameId(gameId)
+    }
+
     fun loadGameAsSpectator(startEventId: String) {
         scope.launch(Dispatchers.Default) {
             state.setBroadcastStatus(ChessBroadcastStatus.Syncing(0f))

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

@@ -201,6 +201,7 @@ fun LiveChessGameScreen(
     onResign: () -> Unit,
     isSpectatorOverride: Boolean? = null,
     onGameEndDismiss: (() -> Unit)? = null,
+    onLeaveSpectating: (() -> Unit)? = null,
     whiteName: String = "White",
     whiteHex: String = "",
     whiteAvatarUrl: String? = null,
@@ -299,7 +300,7 @@ fun LiveChessGameScreen(
                     }
 
                     isSpectator -> {
-                        SpectatorInfo()
+                        SpectatorInfo(onLeaveSpectating = onLeaveSpectating)
                     }
 
                     else -> {
@@ -547,7 +548,12 @@ private fun GameInfoHeader(
  * Info banner shown when spectating a game
  */
 @Composable
-private fun SpectatorInfo() {
+private fun SpectatorInfo(onLeaveSpectating: (() -> Unit)? = null) {
+    Column(
+        modifier = Modifier.fillMaxWidth(),
+        horizontalAlignment = Alignment.CenterHorizontally,
+        verticalArrangement = Arrangement.spacedBy(8.dp),
+    ) {
         Box(
             modifier =
                 Modifier
@@ -564,6 +570,12 @@ private fun SpectatorInfo() {
                 color = MaterialTheme.colorScheme.onTertiaryContainer,
             )
         }
+        onLeaveSpectating?.let { onLeave ->
+            OutlinedButton(onClick = onLeave) {
+                Text("Leave Game")
+            }
+        }
+    }
 }
 
 /**

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

@@ -281,6 +281,15 @@ fun ChessScreen(
                     },
                     onResign = { viewModel.resign(gameState.startEventId) },
                     isSpectatorOverride = isSpectating,
+                    onLeaveSpectating =
+                        if (isSpectating) {
+                            {
+                                viewModel.stopSpectating(gameState.startEventId)
+                                viewModel.selectGame(null)
+                            }
+                        } else {
+                            null
+                        },
                     compactMode = compactMode,
                     whiteName = viewModel.userMetadataCache.getDisplayName(whitePubkey),
                     whiteHex = whitePubkey,
@@ -614,6 +623,7 @@ private fun DesktopChessGameLayout(
     onMoveMade: (from: String, to: String, san: String) -> Unit,
     onResign: () -> Unit,
     isSpectatorOverride: Boolean? = null,
+    onLeaveSpectating: (() -> Unit)? = null,
     compactMode: Boolean = false,
     whiteName: String = "White",
     whiteHex: String = "",
@@ -860,8 +870,11 @@ private fun DesktopChessGameLayout(
                                     containerColor = MaterialTheme.colorScheme.tertiaryContainer.copy(alpha = 0.5f),
                                 ),
                         ) {
-                            Row(
+                            Column(
                                 modifier = Modifier.padding(16.dp),
+                                verticalArrangement = Arrangement.spacedBy(8.dp),
+                            ) {
+                                Row(
                                     verticalAlignment = Alignment.CenterVertically,
                                     horizontalArrangement = Arrangement.spacedBy(8.dp),
                                 ) {
@@ -871,6 +884,15 @@ private fun DesktopChessGameLayout(
                                         style = MaterialTheme.typography.bodyMedium,
                                     )
                                 }
+                                onLeaveSpectating?.let { onLeave ->
+                                    OutlinedButton(
+                                        onClick = onLeave,
+                                        modifier = Modifier.fillMaxWidth(),
+                                    ) {
+                                        Text("Leave Game")
+                                    }
+                                }
+                            }
                         }
                     }
 

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

@@ -172,7 +172,7 @@ class DesktopChessViewModelNew(
 
     fun loadGameAsSpectator(gameId: String) = logic.loadGameAsSpectator(gameId)
 
-    fun stopSpectating(gameId: String) = logic.state.removeSpectatingGame(gameId)
+    fun stopSpectating(gameId: String) = logic.stopSpectating(gameId)
 
     // ============================================
     // Utility