Fix chat warnings PR: serialization compat and guidelines cleanup

MessageEvent: store type as String not enum — unknown enum constants
cause InvalidObjectException on older clients even for skipped fields.

Remove ILobbyListener default overload, dead isSystemMessage(), inline
imports in test files, trailing periods on comments.

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

Author: MostCromulent

forge-gui-desktop/src/main/java/forge/gui/FNetOverlay.java

@@ -135,7 +135,7 @@ public FTextField getTxtInput(){
         Color playerColor = (skinTextColor != null) ? skinTextColor.getColor() : Color.WHITE;
         StyleConstants.setForeground(playerStyle, playerColor);
 
-        // Warning style: amber/caution color, distinct from blue system / white player.
+        // Warning style: amber/caution color, distinct from blue system / white player
         StyleConstants.setForeground(warningStyle, new Color(230, 160, 50));
 
         window.setTitle(Localizer.getInstance().getMessage("lblChat"));

forge-gui-desktop/src/test/java/forge/net/HeadlessNetworkClient.java

@@ -2,6 +2,7 @@
 
 import forge.game.GameView;
 import forge.gamemodes.net.DeltaPacket;
+import forge.gamemodes.net.ChatMessage;
 import forge.util.IHasForgeLog;
 import forge.gamemodes.match.GameLobby.GameLobbyData;
 import forge.gamemodes.net.client.ClientGameLobby;
@@ -237,7 +238,7 @@ public void update(GameLobbyData state, int slot) {
         }
 
         @Override
-        public void message(String source, String message, forge.gamemodes.net.ChatMessage.MessageType type) {
+        public void message(String source, String message, ChatMessage.MessageType type) {
             netLog.info("Chat: {}: {}", source, message);
         }
 

forge-gui-desktop/src/test/java/forge/net/UnifiedNetworkHarness.java

@@ -11,6 +11,7 @@
 import forge.gamemodes.match.HostedMatch;
 import forge.gamemodes.match.LobbySlot;
 import forge.gamemodes.match.LobbySlotType;
+import forge.gamemodes.net.ChatMessage;
 import forge.util.IHasForgeLog;
 import forge.gamemodes.net.NetworkByteTracker;
 import forge.gamemodes.net.NetworkLogConfig;
@@ -496,7 +497,7 @@ public void update(GameLobbyData state, int slot) {
             }
 
             @Override
-            public void message(String source, String message, forge.gamemodes.net.ChatMessage.MessageType type) {
+            public void message(String source, String message, ChatMessage.MessageType type) {
                 netLog.info("Lobby message from {}: {}", source, message);
             }
 

forge-gui/src/main/java/forge/gamemodes/net/ChatMessage.java

@@ -42,10 +42,6 @@ public boolean isLocal() {
         return source == null || source.equals(prefs.getPref(FPref.PLAYER_NAME));
     }
 
-    public boolean isSystemMessage() {
-        return type == MessageType.SYSTEM;
-    }
-
     public MessageType getType() {
         return type;
     }

forge-gui/src/main/java/forge/gamemodes/net/event/MessageEvent.java

@@ -7,16 +7,19 @@ public final class MessageEvent implements NetEvent {
     private static final long serialVersionUID = 1700060210647684186L;
 
     private final String source, message;
-    // Null for backwards compat with pre-WARNING-tag senders; getType() normalizes.
-    private final ChatMessage.MessageType type;
+    // String not enum — unknown enum constants cause InvalidObjectException on older clients
+    private final String type;
 
     public MessageEvent(final String message) {
-        this(null, message, null);
+        this(null, message, (String) null);
     }
     public MessageEvent(final String source, final String message) {
-        this(source, message, null);
+        this(source, message, (String) null);
     }
     public MessageEvent(final String source, final String message, final ChatMessage.MessageType type) {
+        this(source, message, type != null ? type.name() : null);
+    }
+    private MessageEvent(final String source, final String message, final String type) {
         this.source = source;
         this.message = message;
         this.type = type;
@@ -39,8 +42,14 @@ public String getMessage() {
     }
 
     public ChatMessage.MessageType getType() {
-        if (type != null) return type;
-        return source == null ? ChatMessage.MessageType.SYSTEM : ChatMessage.MessageType.PLAYER;
+        if (type == null) {
+            return source == null ? ChatMessage.MessageType.SYSTEM : ChatMessage.MessageType.PLAYER;
+        }
+        try {
+            return ChatMessage.MessageType.valueOf(type);
+        } catch (IllegalArgumentException e) {
+            return ChatMessage.MessageType.SYSTEM;
+        }
     }
 
     @Override

forge-gui/src/main/java/forge/interfaces/ILobbyListener.java

@@ -5,13 +5,7 @@
 import forge.gamemodes.net.client.ClientGameLobby;
 
 public interface ILobbyListener {
-    // type may be null from older peers — implementations should fall back to source-based inference.
     void message(String source, String message, ChatMessage.MessageType type);
-
-    default void message(String source, String message) {
-        message(source, message, null);
-    }
-
     void update(GameLobbyData state, int slot);
     void close();
     ClientGameLobby getLobby();