2.10.14: warn when Steam launch options run the game with the Mono debugger (costs FPS)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

MultiplayerManager.cs

@@ -72,6 +72,20 @@ namespace MSCO
 
         void ToastJoined(string name) { toasts.Add(name, "joined the game", UiTheme.Online); }
 
+        /// <summary>
+        /// Steam-Startoptionen mit "--doorstop-mono-debug-enabled true" (vom MSCLoader-Entwicklermodus): das ganze Spiel läuft
+        /// mit Mono-Debugger und spürbar langsamer. Einmal deutlich melden.
+        /// </summary>
+        void WarnDebugLaunchOptions()
+        {
+            string[] args = System.Environment.GetCommandLineArgs();
+            int i = System.Array.FindIndex(args, a => a.Equals("--doorstop-mono-debug-enabled", System.StringComparison.OrdinalIgnoreCase));
+            if (i < 0 || i + 1 >= args.Length || !(args[i + 1] == "true" || args[i + 1] == "1")) return;
+            MscoLog.Warning("[MSCO] The game runs with the Mono debugger (Steam launch options: --doorstop-mono-debug-enabled true) - " +
+                            "that costs FPS. In Steam: My Summer Car -> Properties -> General -> Launch options: delete everything.");
+            toasts.Add("Debug mode costs FPS", "Clear the Steam launch options of My Summer Car", UiTheme.Gold);
+        }
+
         const string OutdatedServerText = "This server is outdated - it is missing MSCO security updates. You can join again once its owner has updated it (web panel -> Update).";
         const string OutdatedHostText = "The host uses an outdated MSCO version that is missing security updates. Ask them to update " +
                                         "MSCO (start the game once through the MSCO Launcher), then join again.";
@@ -112,6 +126,7 @@ namespace MSCO
         {
             Application.runInBackground = true;
             playerName = PlayerPrefs.GetString(PrefName, System.Environment.UserName);
+            WarnDebugLaunchOptions();
             // Neue Ankündigung der MSCO-Admins, während man spielt: kurz einblenden und in die Konsole (F7)
             SiteStatus.NewAnnouncement += a =>
             {