fix(folio-spec): pick account card via seeded from(), not Math.random

Math.random() breaks --seed reproducibility. The verifier's seeded
RNG flows through from(), so re-running a seed now produces the
same card pick sequence.

examples/folio/sanderling/spec.ts

@@ -162,7 +162,7 @@ const addTxn = actions(() => {
   if (route.current === "home") {
     const cards = accountCards.current;
     if (cards.length === 0) return [];
-    return [Tap({ on: cards[Math.floor(Math.random() * cards.length)] })];
+    return [Tap({ on: from(cards).generate() })];
   }
   if (route.current === "ledger") {
     const btn = addTxnButton.current;