Seal/abstract/virtual everything (#6739)

Content.Client/Lobby/LobbyState.cs

@@ -26,7 +26,7 @@ using Robust.Shared.ViewVariables;
 
 namespace Content.Client.Lobby
 {
-    public class LobbyState : Robust.Client.State.State
+    public sealed class LobbyState : Robust.Client.State.State
     {
         [Dependency] private readonly IBaseClient _baseClient = default!;
         [Dependency] private readonly IClientConsoleHost _consoleHost = default!;

Content.Client/Lobby/UI/LobbyCharacterPreviewPanel.cs

@@ -21,7 +21,7 @@ using static Robust.Client.UserInterface.Controls.BoxContainer;
 
 namespace Content.Client.Lobby.UI
 {
-    public class LobbyCharacterPreviewPanel : Control
+    public sealed class LobbyCharacterPreviewPanel : Control
     {
         private readonly IEntityManager _entMan;
         private readonly IClientPreferencesManager _preferencesManager;

Content.Client/Lobby/UI/LobbyGui.xaml.cs

@@ -40,7 +40,7 @@ namespace Content.Client.Lobby.UI
         }
     }
 
-    public class LobbyPlayerList : Control
+    public sealed class LobbyPlayerList : Control
     {
         private readonly ScrollContainer _scroll;
         private readonly BoxContainer _vBox;