fix: restore npc spawning via the otapi create hook

Author: bulkinglb

TerrariaServerAPI/TerrariaApi.Server/Hooking/NpcHooks.cs

@@ -22,6 +22,7 @@ public static void AttachTo(HookManager hookManager)
 		HookEvents.Terraria.NPC.Transform += OnTransform;
 		HookEvents.Terraria.NPC.AI += OnAI;
 
+		Hooks.NPC.Create += OnCreate;
 		Hooks.NPC.Spawn += OnSpawn;
 		Hooks.NPC.DropLoot += OnDropLoot;
 		Hooks.NPC.BossBag += OnBossBagItem;
@@ -70,6 +71,16 @@ static void OnTransform(NPC npc, HookEvents.Terraria.NPC.TransformEventArgs args
 			args.ContinueExecution = false;
 	}
 
+	static void OnCreate(object sender, Hooks.NPC.CreateEventArgs e)
+	{
+		// OTAPI 3.3.12 moved slot assignment into this hook, but its fallback returns a bare
+		// `new NPC()` that never reaches Main.npc, so every spawn is discarded. NewNPCInstanceInSlot
+		// is the engine's own factory: it stores the instance, sets whoAmI and bumps the slot
+		// generation clients use to tell recycled NPCs apart.
+		if (e.Npc == null && e.Slot >= 0 && e.Slot < Main.npc.Length)
+			e.Npc = NPC.NewNPCInstanceInSlot(e.Slot, (byte)e.Generation);
+	}
+
 	static void OnSpawn(object sender, Hooks.NPC.SpawnEventArgs e)
 	{
 		if (e.Result == HookResult.Cancel)