decouple briefing from traitor (#19668)

Co-authored-by: deltanedas <@deltanedas:kde.org>

Content.Server/Roles/RoleBriefingComponent.cs

@@ -0,0 +1,11 @@
+namespace Content.Server.Roles;
+
+/// <summary>
+/// Adds a briefing to the character info menu, does nothing else.
+/// </summary>
+[RegisterComponent]
+public sealed partial class RoleBriefingComponent : Component
+{
+    [DataField("briefing"), ViewVariables(VVAccess.ReadWrite)]
+    public string Briefing;
+}