Restore regular mob MASK_PET aggro scan

The scan was removed as dead code, but creature runes list Pet in
rune_enemy_monster_types, so monsters are meant to aggro summoned pets.
Restored unchanged; it stays inactive until MASK_PET is set from the
rune data.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/engine/mobileAI/MobAI.java

@@ -628,6 +628,25 @@ public class MobAI {
                     return;
                 }
             }
+
+            if (aiAgent.getCombatTarget() == null) {
+
+                //look for pets to aggro if no players found to aggro
+
+                HashSet<AbstractWorldObject> awoList = WorldGrid.getObjectsInRangePartial(aiAgent, MobAIThread.AI_BASE_AGGRO_RANGE, MBServerStatics.MASK_PET);
+
+                for (AbstractWorldObject awoMob : awoList) {
+
+                    // exclude self.
+
+                    if (aiAgent.equals(awoMob))
+                        continue;
+
+                    Mob aggroMob = (Mob) awoMob;
+                    aiAgent.setCombatTarget(aggroMob);
+                    return;
+                }
+            }
         } catch (Exception e) {
             Logger.error(e, aiAgent.getObjectUUID() + " " + aiAgent.getName() + " Failed At: CheckForAggro");
         }