Initial commit: Ananta CBT 4229938 private server with all fixes

Ananta.Server/Ananta.Handlers/LoginGate/GateSessionHub.cs

@@ -0,0 +1,29 @@
+using Ananta.SDK.Network;
+
+namespace Ananta.Server.Handlers.LoginGate;
+
+/// <summary>
+/// Tracks the authenticated Gate socket. IMasterToClient is routed to ServerMark.Gate
+/// in client build 4229938, so server-pushed master RPCs must use this session, not Game.
+/// </summary>
+internal sealed class GateSessionHub
+{
+    private TcpSession? _current;
+    private long _lastSeenTicks;
+
+    internal TcpSession? Current => Volatile.Read(ref _current);
+    internal DateTimeOffset? LastSeenUtc
+    {
+        get
+        {
+            var ticks = Interlocked.Read(ref _lastSeenTicks);
+            return ticks == 0 ? null : new DateTimeOffset(ticks, TimeSpan.Zero);
+        }
+    }
+
+    internal void Touch(TcpSession session)
+    {
+        Volatile.Write(ref _current, session);
+        Interlocked.Exchange(ref _lastSeenTicks, DateTimeOffset.UtcNow.Ticks);
+    }
+}