fix(spells): make the bleed spell bleed

PF1e (SRD spells/bleed.md): "Saving Throw Will negates" and the target takes 1 point of damage per round. Two divergences: the JSON declared a Fortitude save, and the bleeding condition never set the engine's bleed_damage field, so the spell was a no-op. Bleed now saves Will; _apply_condition_effect sets bleed_damage = 1 when a spell applies bleeding, and _decrement_durations lands the final tick as the last bleeding condition expires before clearing the field (heal-path clearing already existed in _stop_bleeding). README updated.

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

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

src/pf1e_simulator/combat.py

@@ -1732,17 +1732,31 @@ class CombatEngine:
         return speed_mult
 
     def _decrement_durations(self, state: CombatantState) -> None:
-        """Decrement duration rounds for buffs and conditions; remove expired ones."""
+        """Decrement duration rounds for buffs and conditions; remove expired ones.
+
+        A bleeding condition's last round ends with its bleed tick: the DoT
+        lives on ``bleed_damage`` (CRB Conditions — bleeding), so the final
+        damage is applied as the last condition instance expires and the
+        field is cleared (mirrors ``_stop_bleeding`` on healing).
+        """
         state.active_buffs[:] = [
             ActiveBuff(modifiers=b.modifiers, rounds_left=b.rounds_left - 1, source=b.source)
             for b in state.active_buffs
             if b.rounds_left > 1
         ]
-        state.active_conditions[:] = [
+        kept_conditions = [
             ActiveCondition(condition=c.condition, rounds_left=c.rounds_left - 1, source=c.source)
             for c in state.active_conditions
             if c.rounds_left > 1
         ]
+        bleeding_expired = (
+            any(ac.condition.name == "bleeding" for ac in state.active_conditions)
+            and not any(ac.condition.name == "bleeding" for ac in kept_conditions)
+        )
+        state.active_conditions[:] = kept_conditions
+        if bleeding_expired and state.bleed_damage > 0:
+            self._apply_bleed_damage(state)
+            state.bleed_damage = 0
 
     def _turn_gate(self, state: CombatantState) -> bool | None:
         """Start-of-turn effects: bleed tick, confused d% roll, cant_act flag.
@@ -5571,6 +5585,11 @@ class CombatEngine:
                 source=f"spell: {spell_name}",
             )
         )
+        if effect.condition_name == "bleeding":
+            # The bleeding condition's damage-over-time is engine-driven
+            # (CombatantState.bleed_damage, CRB Conditions — bleeding); the
+            # SRD Bleed cantrip (spells/bleed.md) deals 1 bleed damage/round.
+            target.bleed_damage = max(target.bleed_damage, 1)
         return f"{effect.condition_name} ({effect.duration_rounds}r)"
 
     def _apply_heal_effect(