Add C# dedicated server replacement

server/ServerRuntime.cs

@@ -0,0 +1,53 @@
+namespace CommonwealthOnline.Server;
+
+internal sealed class ServerRuntime : IAsyncDisposable
+{
+    private readonly ServerOptions _options;
+    private readonly AuthoritativeServer _server;
+    private readonly TcpServerTransport _tcp;
+    private readonly GnsServerTransport? _gns;
+    private readonly AdminControlServer _admin;
+    private readonly LanDiscoveryService _discovery;
+    private int _started;
+
+    public ServerRuntime(ServerOptions options)
+    {
+        _options = options;
+        _server = new AuthoritativeServer(options);
+        _tcp = new TcpServerTransport(options, _server);
+        _gns = options.EnableGnsTransport ? new GnsServerTransport(options, _server) : null;
+        _admin = new AdminControlServer(_server, options);
+        _discovery = new LanDiscoveryService(_server, options);
+    }
+
+    public AuthoritativeServer Server => _server;
+
+    public void Start()
+    {
+        if (Interlocked.Exchange(ref _started, 1) != 0) return;
+        _admin.Start();
+        try
+        {
+            _tcp.Start();
+            _gns?.Start();
+            try { _discovery.Start(); }
+            catch (Exception ex) { _server.Log($"LAN discovery unavailable on UDP {LanDiscoveryService.DiscoveryPort}: {ex.Message}. Direct connections still work.", "warning"); }
+        }
+        catch
+        {
+            DisposeAsync().AsTask().GetAwaiter().GetResult();
+            throw;
+        }
+        _server.Log($"Commonwealth Online server listening on {_options.Host}:{_options.Port}");
+        _server.Log($"Protocol v{ProtocolConstants.ProtocolVersion} negotiation enabled; legacy TCP clients remain temporarily compatible.");
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        if (_gns is not null) await _gns.DisposeAsync();
+        await _tcp.DisposeAsync();
+        await _discovery.DisposeAsync();
+        await _admin.DisposeAsync();
+        await _server.DisposeAsync();
+    }
+}