fix antag selection being evil (#28197)

* fix antag selection being evil

* fix test

* untroll the other tests

* remove role timer troll

* Allow tests to modify antag preferences

* Fix antag selection

* Misc test fixes

* Add AntagPreferenceTest

* Fix lazy mistakes

* Test cleanup

* Try stop players in lobbies from being assigned mid-round antags

* ranting

* I am going insane

---------

Co-authored-by: deltanedas <@deltanedas:kde.org>
Co-authored-by: ElectroJr <leonsfriedrich@gmail.com>

Content.Shared/Antag/AntagAcceptability.cs

@@ -22,6 +22,14 @@ public enum AntagAcceptability
 
 public enum AntagSelectionTime : byte
 {
+    /// <summary>
+    /// Antag roles are assigned before players are assigned jobs and spawned in.
+    /// This prevents antag selection from happening if the round is on-going.
+    /// </summary>
     PrePlayerSpawn,
+
+    /// <summary>
+    /// Antag roles get assigned after players have been assigned jobs and have spawned in.
+    /// </summary>
     PostPlayerSpawn
 }