NPC refactor (#10122)

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

Content.Server/NPC/HTN/PrimitiveTasks/Operators/WaitOperator.cs

@@ -0,0 +1,36 @@
+namespace Content.Server.NPC.HTN.PrimitiveTasks.Operators;
+
+/// <summary>
+/// Waits the specified amount of time. Removes the key when finished.
+/// </summary>
+public sealed class WaitOperator : HTNOperator
+{
+    /// <summary>
+    /// Blackboard key for the time we'll wait for.
+    /// </summary>
+    [ViewVariables, DataField("key", required: true)] public string Key = string.Empty;
+
+    public override HTNOperatorStatus Update(NPCBlackboard blackboard, float frameTime)
+    {
+        if (!blackboard.TryGetValue<float>(Key, out var timer))
+        {
+            return HTNOperatorStatus.Finished;
+        }
+
+        timer -= frameTime;
+        blackboard.SetValue(Key, timer);
+
+        return timer <= 0f ? HTNOperatorStatus.Finished : HTNOperatorStatus.Continuing;
+    }
+
+    public override void Shutdown(NPCBlackboard blackboard, HTNOperatorStatus status)
+    {
+        base.Shutdown(blackboard, status);
+
+        // The replacement plan may want this value so only dump it if we're successful.
+        if (status != HTNOperatorStatus.BetterPlan)
+        {
+            blackboard.Remove<float>(Key);
+        }
+    }
+}