Fix flaky test

[mizdra]

• packages/codegen/src/runner.test.ts > runCMKInWatchMode > reports diagnostics and emits files on changes
  • test-vitest (22, ubuntu-24.04-arm).txt
  • test (20, windows-11-arm).txt
• packages/codegen/src/runner.test.ts > runCMKInWatchMode > reports system error occurs during watching
  • test-vitest (20, macos-latest)
  • test-vitest (22, macos-latest).txt