docs(fmt): clarify synchronous I/O tradeoff

Author: chenjiahan

packages/rstack/src/fmt/worker.ts

@@ -16,8 +16,8 @@ const hashContent = (content: string | Uint8Array): string =>
   hash('sha256', content, 'base64url').slice(0, 16);
 
 /**
- * Use synchronous direct I/O in workers and the one-file main-thread path to avoid
- * libuv scheduling overhead. This prioritizes throughput over crash-safe replacement.
+ * Synchronous file I/O avoids libuv scheduling overhead in workers and single-file
+ * main-thread runs. This favors throughput over crash-safe file replacement.
  */
 const formatFile = async ({
   file,