fix(Core/Combat): Fix guardians not attacking after threat system port (#25157)

Co-authored-by: blinkysc <blinkysc@users.noreply.github.com>

src/server/scripts/Pet/pet_dk.cpp

@@ -306,6 +306,8 @@ struct npc_pet_dk_army_of_the_dead : public AggressorAI
 {
     npc_pet_dk_army_of_the_dead(Creature* creature) : AggressorAI(creature) { }
 
+    // Restrict MoveInLineOfSight aggro to targets already fighting our owner,
+    // so ghouls don't pull extra packs on their own.
     bool CanAIAttack(Unit const* target) const override
     {
         if (!target)
@@ -315,6 +317,26 @@ struct npc_pet_dk_army_of_the_dead : public AggressorAI
             return false;
         return AggressorAI::CanAIAttack(target);
     }
+
+    // Owner started attacking a target — engage immediately.
+    // We bypass OnOwnerCombatInteraction because CanStartAttack -> CanAIAttack
+    // may reject the target before combat refs are established.
+    void OwnerAttacked(Unit* target) override
+    {
+        if (!target || !me->IsAlive() || me->HasReactState(REACT_PASSIVE))
+            return;
+        if (me->IsValidAttackTarget(target))
+            AttackStart(target);
+    }
+
+    // Owner was attacked — help defend.
+    void OwnerAttackedBy(Unit* attacker) override
+    {
+        if (!attacker || !me->IsAlive() || me->HasReactState(REACT_PASSIVE))
+            return;
+        if (me->IsValidAttackTarget(attacker))
+            AttackStart(attacker);
+    }
 };
 
 struct npc_pet_dk_dancing_rune_weapon : public NullCreatureAI