fix(combat): correct spell DC formula

src/pf1e_simulator/models.py

@@ -113,3 +113,5 @@ class Combatant(_FrozenModel):
     notes: str = ""
     features: list[AbilitySpec] = []
     spells: list[str] = []
+    casting_ability: str = "wis"  # ability used for spell DCs: str/dex/con/int/wis/cha
+    resources: dict[str, int] = Field(default_factory=dict)  # resource pools per combat