NPC refactor (#10122)

Co-authored-by: metalgearsloth <metalgearsloth@gmail.com>

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

@@ -0,0 +1,11 @@
+namespace Content.Server.NPC.HTN.Preconditions;
+
+public sealed class KeyExistsPrecondition : HTNPrecondition
+{
+    [DataField("key", required: true)] public string Key = string.Empty;
+
+    public override bool IsMet(NPCBlackboard blackboard)
+    {
+        return blackboard.ContainsKey(Key);
+    }
+}