fix(combat): _find_ally_needing_heal counts only living allies (SRD Channel Energy: heal mode heals living creatures, positive energy never heals undead) - an undead ally below half triggered heal mode, spending the channel to heal nobody; + trigger regression test

src/pf1e_simulator/combat.py

@@ -8311,15 +8311,21 @@ def _find_heal_spell(engine: CombatEngine, spells_known: list[str]) -> str | Non
 
 
 def _find_ally_needing_heal(engine: CombatEngine, caster: CombatantState) -> CombatantState | None:
-    """Find an ally below half HP.
+    """Find a living ally below half HP.
 
     ``hp * 2 < hp_max`` is strictly-below-half for every hp_max; the old
     ``hp < hp_max // 2`` floored the threshold (hp_max 5 -> 2), so a level-1
     character at 2/5 hp counted as healthy.
+
+    Living-only (SRD Channel Energy: heal mode heals living creatures; undead
+    take damage from positive energy, never healing): an undead ally below
+    half must not trigger the heal paths - channel heal would spend the
+    channel without helping it, and a cure spell would hurt it.
     """
     for ally_state in engine.states:
         below_half = ally_state.hp * 2 < ally_state.combatant.hp_max
-        if ally_state.side == caster.side and ally_state.active and below_half:
+        living = ally_state.combatant.creature_type == "living"
+        if ally_state.side == caster.side and ally_state.active and living and below_half:
             return ally_state
     return None