fix(rules): cure spells damage undead instead of healing

SRD Cure Light Wounds: 'Since undead are powered by negative energy,
this spell deals damage to them instead of curing their wounds. An
undead creature can apply spell resistance, and can attempt a Will save
to take half damage.'

- _apply_heal_effect takes the rolled save; an undead target takes the
  rolled healing as damage (halved on a successful save; SR already
  resolved upstream, DR never applies to spell energy, no bleeding stop
  or stabilization). Living targets are bit-identical.
- cure_light/cure_moderate descriptions fixed: the SRD save line is
  'Will half (harmless)', not 'negates'.
- Deafened 20% verbal spell failure DEFERRED to the README « Limites
  hors perimetre »: SpellSpec carries no components data (would need a
  verbal flag on all 108 spells) and sound-based Perception is not
  modeled either.

src/pf1e_simulator/combat.py

@@ -6287,7 +6287,7 @@ class CombatEngine:
         if isinstance(effect, HealEffect):
             return self._apply_heal_effect(
                 effect, target, caster_level=caster.combatant.level,
-                empower=empower, maximize=maximize,
+                empower=empower, maximize=maximize, saved=saved,
             )
         return self._apply_buff_effect(effect, target, spell_name=spell_name)
 
@@ -6475,6 +6475,7 @@ class CombatEngine:
         caster_level: int,
         empower: bool,
         maximize: bool,
+        saved: bool,
     ) -> str:
         formula = effect.effective_formula(caster_level)
         heal = formula.roll(self._rng)
@@ -6482,6 +6483,17 @@ class CombatEngine:
             heal = formula.max_value()
         if empower:
             heal = int(heal * 1.5)
+        if target.combatant.creature_type == "undead":
+            # PF1e (SRD "Cure Light Wounds"): "Since undead are powered by
+            # negative energy, this spell deals damage to them instead of
+            # curing their wounds. An undead creature can apply spell
+            # resistance, and can attempt a Will save to take half damage."
+            # SR is resolved upstream (_spell_delivery_blocked); the rolled
+            # save halves here. Cure damage is spell energy: never reduced by
+            # DR, and it does not stop bleeding or stabilize.
+            dmg = heal // 2 if saved else heal
+            target.hp -= dmg
+            return f"{dmg} damage (undead)"
         old_hp = target.hp
         target.hp = min(target.hp + heal, target.combatant.hp_max)
         # PF1e (CRB, Stable Characters and Recovery): "If any sort of healing