fix: scale monster DEF with floor level like HP/ATK

entity/monster.go

@@ -51,13 +51,14 @@ func NewMonster(mt MonsterType, floor int) *Monster {
 	}
 	hp := int(math.Round(float64(base.HP) * scale))
 	atk := int(math.Round(float64(base.ATK) * scale))
+	def := int(math.Round(float64(base.DEF) * scale))
 	return &Monster{
 		Name:   base.Name,
 		Type:   mt,
 		HP:     hp,
 		MaxHP:  hp,
 		ATK:    atk,
-		DEF:    base.DEF,
+		DEF:    def,
 		IsBoss: base.IsBoss,
 	}
 }

entity/monster_test.go

@@ -23,3 +23,16 @@ func TestBossStats(t *testing.T) {
 		t.Errorf("Boss5: got HP=%d ATK=%d DEF=%d, want 150/15/8", boss.HP, boss.ATK, boss.DEF)
 	}
 }
+
+func TestMonsterDEFScaling(t *testing.T) {
+	// Slime base DEF=1, minFloor=1. At floor 5, scale = 1.15^4 ≈ 1.749
+	m := NewMonster(MonsterSlime, 5)
+	if m.DEF <= 1 {
+		t.Errorf("Slime DEF at floor 5 should be scaled above base 1, got %d", m.DEF)
+	}
+	// Boss DEF should NOT scale
+	boss := NewMonster(MonsterBoss5, 5)
+	if boss.DEF != 8 {
+		t.Errorf("Boss5 DEF should be base 8, got %d", boss.DEF)
+	}
+}