[codex] Add Windows support

[divitsheth]

Summary

• add Windows Task Scheduler support for almanac automation install|status|uninstall
• make setup, doctor, uninstall, install-path detection, and Codex command launching platform-aware
• add Windows GitHub Actions coverage across Node 20 and Node 22
• document the Windows scheduler and test-portability gotchas in Almanac notes

Validation

• npm run lint
• npm run build
• npm test on clean GitHub Actions matrix
• GitHub Actions: https://github.com/AlmanacCode/codealmanac/actions/runs/25848688754

Notes

• The branch was cut from main at 7a7d615 (v0.2.23).
• Local unstaged viewer files are not part of this PR.