Launcher can be minimized to a small bar in the start menu

A '-' button collapses the fullscreen launcher into a small MSCO bar at the
top; the game's start menu is visible and clickable again and its music is
unmuted. Clicking the bar opens the launcher; prompts (disconnected,
reconnecting, join confirmation, version warning) open it automatically.

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

MultiplayerManager.cs

@@ -65,6 +65,7 @@ namespace MSCO
         readonly TrafficSync traffic = new TrafficSync();
         readonly HingeSync hinges = new HingeSync();
         readonly ControlSync controls = new ControlSync();
+        bool lobbyWasMinimized;
         float nextControlResync;
         readonly Toasts toasts = new Toasts();
         float nextNeedsSend;
@@ -972,7 +973,13 @@ namespace MSCO
             {
                 nextMenuButtonCheck = Time.realtimeSinceStartup + 0.5f;
                 menuButtonsHidden = MenuHelper.HideGameMenuButtons() > 0;
-                MenuHelper.MuteMenuAudio(); // Launcher im Vollbild: Menü-Musik/-Geräusche aus
+                if (!lobby.Minimized) MenuHelper.MuteMenuAudio(); // Launcher im Vollbild: Menü-Musik/-Geräusche aus
+            }
+            // Launcher eingeklappt: Menü-Musik wieder an; aufgeklappt: wieder aus
+            if (MenuHelper.InMenu && lobby.Minimized != lobbyWasMinimized)
+            {
+                lobbyWasMinimized = lobby.Minimized;
+                if (lobby.Minimized) MenuHelper.UnmuteMenuAudio(); else MenuHelper.MuteMenuAudio();
             }
             UpdateOverlayKeys();
             PersistPendingState(); // Kick-Grund / Neu-Verbinden über das Neuladen der Mods hinweg merken