refactor(Core/Combat): Port TrinityCore heap-based threat system (#24715)

Co-authored-by: blinkysc <blinkysc@users.noreply.github.com>
Co-authored-by: Treeston <treeston.mmoc@gmail.com>
Co-authored-by: killerwife <killerwife@gmail.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/server/game/Grids/Notifiers/GridNotifiers.h

@@ -1158,12 +1158,9 @@ namespace Acore
             if (!u->IsWithinLOSInMap(i_enemy))
                 return;
 
-            if (u->AI())
-            {
-                u->SetNoCallForHelp(true); // avoid recursive call for help causing stack overflow
-                u->AI()->AttackStart(i_enemy);
-                u->SetNoCallForHelp(false);
-            }
+            u->SetNoCallForHelp(true); // avoid recursive call for help causing stack overflow
+            u->EngageWithTarget(i_enemy);
+            u->SetNoCallForHelp(false);
         }
     private:
         Unit* const i_funit;