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.

tests/test_bleeding_confused.py

@@ -103,7 +103,7 @@ def test_heal_spell_clears_bleed() -> None:
     a.conditions.append(BLEEDING)
     result = eng._apply_heal_effect(
         HealEffect(formula=parse_dice("1d8")), a, caster_level=1,
-        empower=False, maximize=False,
+        empower=False, maximize=False, saved=False,
     )
     assert result == "+5 HP"
     assert a.hp == 55