News UI overhaul and PDA notifications (#19610)

Content.Shared/CartridgeLoader/SharedCartridgeLoaderSystem.cs

@@ -1,6 +1,5 @@
 using Content.Shared.Containers.ItemSlots;
 using Robust.Shared.Containers;
-using Robust.Shared.Network;
 
 namespace Content.Shared.CartridgeLoader;
 
@@ -124,3 +123,11 @@ public sealed class CartridgeUiReadyEvent : EntityEventArgs
         Loader = loader;
     }
 }
+
+/// <summary>
+/// Gets sent by the cartridge loader system to the cartridge loader entity so another system
+/// can handle displaying the notification
+/// </summary>
+/// <param name="Message">The message to be displayed</param>
+[ByRefEvent]
+public record struct CartridgeLoaderNotificationSentEvent(string Header, string Message);