refactor(src): split oversized modules

src/cron/service/locked.ts

@@ -0,0 +1,14 @@
+import type { CronServiceState } from "./state.js";
+
+export async function locked<T>(
+  state: CronServiceState,
+  fn: () => Promise<T>,
+): Promise<T> {
+  const next = state.op.then(fn, fn);
+  // Keep the chain alive even when the operation fails.
+  state.op = next.then(
+    () => undefined,
+    () => undefined,
+  );
+  return (await next) as T;
+}