fix(rules): Extend Spell doubles SummonEffect duration (SRD extend-spell: lasts twice as long; summon's 1 round/level is neither instantaneous, concentration nor permanent)

src/pf1e_simulator/combat.py

@@ -7165,8 +7165,6 @@ class CombatEngine:
         self, effect: SpellEffect, *, has_extend: bool
     ) -> SpellEffect:
         """Apply Extend Spell to one effect (recursing into AreaEffect sub-effects)."""
-        if isinstance(effect, (DamageEffect, HealEffect)):
-            return effect
         if isinstance(effect, ConditionEffect):
             duration = effect.duration_rounds * 2 if has_extend else effect.duration_rounds
             per_level = (
@@ -7210,6 +7208,23 @@ class CombatEngine:
                 duration_rounds_per_level=duration,
                 half_on_save=effect.half_on_save,
             )
+        if isinstance(effect, SummonEffect):
+            # PF1e (SRD feats/extend-spell.md): "An extended spell lasts
+            # twice as long as normal. A spell with a duration of
+            # concentration, instantaneous, or permanent is not affected" -
+            # summon monster's "1 round/level (D)" is none of those, so
+            # Extend doubles it (both the fixed and the per-level form).
+            duration = effect.duration_rounds * 2 if has_extend else effect.duration_rounds
+            per_level = (
+                effect.duration_rounds_per_level * 2
+                if has_extend
+                else effect.duration_rounds_per_level
+            )
+            return SummonEffect(
+                creature=effect.creature,
+                duration_rounds=duration,
+                duration_rounds_per_level=per_level,
+            )
         if isinstance(effect, AreaEffect):
             return AreaEffect(
                 shape=effect.shape,