feat(rules): scale healing spells with caster level

PF1e (SRD spells/cure-light-wounds.md): 'cures 1d8 points of damage +1
point per caster level (maximum +5)'; (spells/cure-moderate-wounds.md):
'cures 2d8 points of damage +1 point per caster level (maximum +10)'.
A HealEffect now carries the same DamageFlatScaling spec as damage
effects (S1b) and resolves it through effective_formula(caster_level)
at cast time, so the flat bonus grows with the caster and stops at the
stated cap. The engine passes the caster's level into _apply_heal_effect
(required keyword: no silent level-0 under-heal); Maximize Spell
maximizes the scaled formula. Cure Light/Moderate Wounds ship the SRD
values; inflict_light_wounds already carried its scaling_flat.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/pf1e_simulator/combat.py

@@ -6202,7 +6202,10 @@ class CombatEngine:
         if isinstance(effect, ConditionEffect):
             return self._apply_condition_effect(effect, target, saved=saved, spell_name=spell_name)
         if isinstance(effect, HealEffect):
-            return self._apply_heal_effect(effect, target, empower=empower, maximize=maximize)
+            return self._apply_heal_effect(
+                effect, target, caster_level=caster.combatant.level,
+                empower=empower, maximize=maximize,
+            )
         return self._apply_buff_effect(effect, target, spell_name=spell_name)
 
     def _apply_damage_effect(
@@ -6386,12 +6389,14 @@ class CombatEngine:
         effect: HealEffect,
         target: CombatantState,
         *,
+        caster_level: int,
         empower: bool,
         maximize: bool,
     ) -> str:
-        heal = effect.formula.roll(self._rng)
+        formula = effect.effective_formula(caster_level)
+        heal = formula.roll(self._rng)
         if maximize:
-            heal = effect.formula.max_value()
+            heal = formula.max_value()
         if empower:
             heal = int(heal * 1.5)
         old_hp = target.hp