Clean up new HTNs tasks (#28469)

* Clean up new HTNs tasks

* Added docs to math operations

Content.Server/NPC/HTN/Preconditions/KeyExistsPrecondition.cs

@@ -1,8 +1,13 @@
 namespace Content.Server.NPC.HTN.Preconditions;
 
+/// <summary>
+/// Checks for the presence of the value by the specified <see cref="KeyExistsPrecondition.Key"/> in the <see cref="NPCBlackboard"/>.
+/// Returns true if there is a value.
+/// </summary>
 public sealed partial class KeyExistsPrecondition : HTNPrecondition
 {
-    [DataField("key", required: true)] public string Key = string.Empty;
+    [DataField(required: true), ViewVariables]
+    public string Key = string.Empty;
 
     public override bool IsMet(NPCBlackboard blackboard)
     {