Seal/abstract/virtual everything (#6739)

Content.Client/Items/Components/ItemComponent.cs

@@ -6,5 +6,6 @@ namespace Content.Client.Items.Components
 {
     [RegisterComponent]
     [ComponentReference(typeof(SharedItemComponent))]
+    [Virtual]
     public class ItemComponent : SharedItemComponent { }
 }

Content.Client/Items/Components/ItemStatusComponent.cs

@@ -3,7 +3,7 @@ using Robust.Shared.GameObjects;
 namespace Content.Client.Items.Components
 {
     [RegisterComponent]
-    public class ItemStatusComponent : Component
+    public sealed class ItemStatusComponent : Component
     {
     }
 }

Content.Client/Items/Managers/ItemSlotManager.cs

@@ -18,7 +18,7 @@ using Robust.Shared.Timing;
 
 namespace Content.Client.Items.Managers
 {
-    public class ItemSlotManager : IItemSlotManager
+    public sealed class ItemSlotManager : IItemSlotManager
     {
         [Dependency] private readonly IGameTiming _gameTiming = default!;
         [Dependency] private readonly IEntitySystemManager _entitySystemManager = default!;

Content.Client/Items/UI/ItemSlotButton.cs

@@ -16,6 +16,7 @@ using Robust.Shared.Utility;
 
 namespace Content.Client.Items.UI
 {
+    [Virtual]
     public class ItemSlotButton : Control, IEntityEventSubscriber
     {
         private const string HighlightShader = "SelectionOutlineInrange";

Content.Client/Items/UI/ItemStatusPanel.cs

@@ -18,7 +18,7 @@ using static Robust.Client.UserInterface.Controls.BoxContainer;
 
 namespace Content.Client.Items.UI
 {
-    public class ItemStatusPanel : Control
+    public sealed class ItemStatusPanel : Control
     {
         [Dependency] private readonly IEntityManager _entityManager = default!;