feat: add world chat UI

Server/Gateway/ServerLoop.cs

@@ -21,6 +21,7 @@ namespace XWorld.Server.Gateway
         private readonly Matchmaker _matchmaker;
         private readonly ChannelsNS.Channel<ServerCommand> _cmds =
             ChannelsNS.Channel.CreateUnbounded<ServerCommand>();
+        private const int MaxWorldChatTextLength = 200;
         private readonly Dictionary<string, List<int>> _roomPlayers = new Dictionary<string, List<int>>();
         private readonly Dictionary<int, LobbyPlayerMsg> _lobbyPlayers = new Dictionary<int, LobbyPlayerMsg>();
         private readonly Dictionary<string, int> _playerCountCache = new Dictionary<string, int>(); // "gameId@version" -> playerCount
@@ -156,6 +157,9 @@ namespace XWorld.Server.Gateway
                 case FrameworkOpcode.LobbyLeave:
                     if (_lobbyPlayers.Remove(pid)) BroadcastLobbyState();
                     break;
+                case FrameworkOpcode.WorldChatSend:
+                    HandleWorldChatSend(pid, frame.Payload);
+                    break;
             }
         }
 
@@ -213,6 +217,41 @@ namespace XWorld.Server.Gateway
             }
         }
 
+        private void HandleWorldChatSend(int pid, byte[] payload)
+        {
+            if (!_sessions.IsConnected(pid))
+            {
+                return;
+            }
+
+            var req = WorldChatSendMsg.Decode(payload);
+            string text = (req.Text ?? string.Empty).Trim();
+            if (text.Length == 0)
+            {
+                return;
+            }
+            if (text.Length > MaxWorldChatTextLength)
+            {
+                text = text.Substring(0, MaxWorldChatTextLength);
+            }
+
+            string name = _lobbyPlayers.TryGetValue(pid, out var player) && !string.IsNullOrWhiteSpace(player.Name)
+                ? player.Name
+                : $"P{pid}";
+            var msg = new WorldChatMessageMsg
+            {
+                PlayerId = pid,
+                PlayerName = name,
+                Text = text,
+                ServerTimeMs = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()
+            };
+            byte[] encoded = msg.Encode();
+            foreach (int targetPid in _sessions.ConnectedPlayerIds())
+            {
+                SendFramework(targetPid, FrameworkOpcode.WorldChatMessage, encoded);
+            }
+        }
+
         private void BroadcastLobbyState()
         {
             if (_lobbyPlayers.Count == 0) return;

Server/Gateway/SessionManager.cs

@@ -38,6 +38,19 @@ namespace XWorld.Server.Gateway
 
         public Session Get(int pid) => _byPid.TryGetValue(pid, out var s) ? s : null;
 
+        public IReadOnlyList<int> ConnectedPlayerIds()
+        {
+            List<int> players = null;
+            foreach (var kv in _byPid)
+            {
+                if (kv.Value.Connected)
+                {
+                    (players ??= new List<int>()).Add(kv.Key);
+                }
+            }
+            return players ?? (IReadOnlyList<int>)Array.Empty<int>();
+        }
+
         /// <summary>移除断线且"严格越过"重连窗口的会话（currentTick - DisconnectedAtTick &gt; windowTicks）。返回被移除的会话；无则空数组。</summary>
         public IReadOnlyList<Session> SweepExpired(long currentTick, long windowTicks)
         {