refactor: extract pick() helper, deduplicate random selection

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/lib/utils.ts

@@ -0,0 +1,10 @@
+/** Pick a random element from an array */
+export function pick<T>(arr: T[]): T {
+  return arr[Math.floor(Math.random() * arr.length)]
+}
+
+/** Wrap an unknown thrown value into an Error */
+export function toError(err: unknown): Error {
+  if (err instanceof Error) return err
+  return new Error(String(err))
+}