Fix Windows Codex plugin test compatibility

[Shemshidin]

Summary

• make npm test avoid direct .mjs execution and shell redirection
• add a cross-platform CLI help smoke test
• replace /dev/stdin privacy probe with a temp registry file
• support Windows PATHEXT command lookup
• sanitize redacted path fields through the generic string redactor

Test

• npm test
• npm pack --dry-run --json

[r266-tech]

Thanks for this, @Shemshidin — these are exactly the right cross-platform fixes. 🙏

A few things I really appreciate here:

• which() PATHEXT support — resolving .EXE/.CMD/.BAT (and / vs \ separators) is the classic gap that silently breaks command lookup on Windows.
• Dropping /dev/stdin for a temp registry file in the privacy probe, plus process.execPath instead of a bare node — both are real portability wins, since neither /dev/stdin nor a node on PATH is guaranteed on Windows.
• The new smoke-cli-help.mjs replacing ... --help >/dev/null — pulling that POSIX-only redirection out of npm test and into a spawnSync is exactly the right call.
• Routing path fields through redactString(redactedPath(...)) is a good defense-in-depth tightening of the redactor.

Two things before this can land:

1. The branch currently conflicts with main (mergeable: CONFLICTING). Could you rebase fix/windows-codex-plugin-tests onto the latest main and push?
2. This repo doesn't report CI checks on PRs, and since this is specifically a Windows-compat change, could you run npm test after the rebase — ideally on Windows — and paste the result here? That gives us a concrete signal the suite is green on the platform you're targeting.

Once it's rebased and green, I'll do a proper review and we should be able to get it merged.

Thanks again for making the CLI Windows-friendly — and sorry for the slow first response here. 🚀