feat(enemy): sistema d'HP declaratiu i nou enemic big_pentagon

data/entities/star/star.yaml

@@ -66,8 +66,10 @@ score: 100
 
 events:
   # STAR: mor al primer impacte, sense passar per wounded.
+  # HP=1 (default): decrement → on_no_health → destroy directe (sense wounded).
   on_hit:
-    - action: apply_impulse
+    - action: decrease_health
+  on_no_health:
     - action: destroy
   on_destroy:
     - action: add_score