fix(spells): apply a shaken effect when a fear save succeeds

ConditionEffect gains save_partial (JSON 'on_success': condition_name + duration_rounds). On a successful save that would otherwise negate, _apply_condition_effect now imposes the weaker condition (SRD fear.md: panicked on a failed Will save, shaken for 1 round on a success). Extended _metamagic_transform_sub to preserve/double it; extracted _impose_condition helper. Updated fear.json, added failed/successful-save and loader tests in test_spells.py, and the README.

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

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

src/pf1e_simulator/combat.py

@@ -6010,23 +6010,44 @@ class CombatEngine:
         spell_name: str,
     ) -> str:
         if saved and effect.save_negates:
+            # PF1e partial save (SRD spells/fear.md): a successful save does
+            # not always spare the target — it may impose a weaker condition
+            # (Fear: shaken for 1 round instead of panicked).
+            if effect.save_partial is not None:
+                name, duration = effect.save_partial
+                applied = self._impose_condition(target, name, duration, spell_name)
+                if not applied:
+                    return ""
+                return f"{name} ({duration}r) (partial save)"
             return f"{effect.condition_name} negated"
-        cond = CONDITIONS_BY_NAME.get(effect.condition_name)
+        return self._impose_condition(
+            target, effect.condition_name, effect.duration_rounds, spell_name
+        )
+
+    def _impose_condition(
+        self,
+        target: CombatantState,
+        condition_name: str,
+        duration_rounds: int,
+        spell_name: str,
+    ) -> str:
+        """Append a timed condition to the target; handle the bleeding DoT."""
+        cond = CONDITIONS_BY_NAME.get(condition_name)
         if cond is None:
             return ""
         target.active_conditions.append(
             ActiveCondition(
                 condition=cond,
-                rounds_left=effect.duration_rounds,
+                rounds_left=duration_rounds,
                 source=f"spell: {spell_name}",
             )
         )
-        if effect.condition_name == "bleeding":
+        if 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)"
+        return f"{condition_name} ({duration_rounds}r)"
 
     def _apply_heal_effect(
         self,
@@ -6222,10 +6243,14 @@ class CombatEngine:
             return effect
         if isinstance(effect, ConditionEffect):
             duration = effect.duration_rounds * 2 if has_extend else effect.duration_rounds
+            partial = effect.save_partial
+            if partial is not None and has_extend:
+                partial = (partial[0], partial[1] * 2)
             return ConditionEffect(
                 condition_name=effect.condition_name,
                 duration_rounds=duration,
                 save_negates=effect.save_negates,
+                save_partial=partial,
             )
         if isinstance(effect, BuffEffect):
             duration = effect.duration_rounds * 2 if has_extend else effect.duration_rounds