This patch fixes the CI test failure that blocked the 1.8.5 publish.
- Fixed the Windows npm invocation test so it creates a real local tarball path instead of relying on a hardcoded Windows-only path.
- This keeps the test valid on Linux GitHub Actions runners, where the previous path did not exist and incorrectly fell back to modelrelay@latest.
- No runtime behavior changes were made in this patch; this release only corrects the cross-platform regression test so publishing can complete.