fix(rules): Toughness is +3 hp below 4 Hit Dice (max(3, level))

src/pf1e_simulator/abilities.py

@@ -49,16 +49,16 @@ def weapon_focus(weapon_name: str) -> AbilitySpec:
     )
 
 
-# Toughness: +1 HP per Hit Die (approximated as +level HP, untyped, CRB)
-# For simplicity at this stage, we model it as a flat HP bonus.
-# The engine doesn't yet compute per-HD bonuses, so the caller sets the value.
+# Toughness (CRB): "+3 hit points. If the character has 4 or more Hit Dice,
+# she gains +1 hit point per Hit Die." => max(3, HD). The engine doesn't yet
+# compute per-HD bonuses, so the caller passes the level.
 def toughness(level: int) -> AbilitySpec:
     return AbilitySpec(
         name="Toughness",
         category="feat",
         source_detail="feat lv1",
         effects=(
-            StatModifier(target="hp", value=level),
+            StatModifier(target="hp", value=max(3, level)),
         ),
     )