Fix simplification rule

The simplification rule in the Rules of Inference Playground now presents both possible outcomes instead of assuming one.

src/components/RulesOfInferencePlayground.tsx

@@ -272,7 +272,7 @@ export default function RulesOfInferencePlayground({ onComplete }: { onComplete?
         case "simplification": {
           // From B ∧ (C ∨ D) derive B or (C ∨ D)
           if (selected.includes("B ∧ (C ∨ D)") && selected.length === 1) {
-            return ["C ∨ D"];
+            return ["B", "C ∨ D"];
           }
           break;
         }