fix(cron): pass Git Bash-friendly paths for Windows .sh jobs

[Bartok9]

Summary

• Convert Windows paths to Git Bash-friendly /c/Users/... form when cron runs .sh/.bash scripts
• Fixes script-not-found errors where backslashes are stripped (C:\Users → C:Users)

Motivation

Closes #60857.

On Windows with Git Bash, _run_job_script passed native Windows backslash paths as bash argv. Git Bash re-parses those backslashes as escapes, so the effective path becomes C:Users... and the job fails with No such file or directory.

Verification

• pytest tests/cron/test_cron_script.py::TestBashFriendlyPath — 3 passed
• Helper unit: C:/Users/.../script.sh → /c/Users/.../script.sh under win32
• Did NOT change: Python cron script execution, scripts-dir containment

Test plan

• Windows + Git Bash: no_agent cron job with script: hello.sh succeeds

[alt-glitch]

This was generated by AI during triage.

Duplicate of #23405 (earliest-open canonical for the Windows git-bash cron .sh backslash-path cluster; same code site cron/scheduler.py::_run_job_script, same MSYS/POSIX-path mechanism). Siblings: #62516, #60892, #44350, #46364. Related spec issue: #60857.

[Bartok9]

Thanks @alt-glitch — agreed, #23405 is the earlier canonical for the git-bash _run_job_script backslash-path cluster. Closing this in favor of it to keep the triage queue clean.

If useful to the canonical, the TestBashFriendlyPath cases here (C:/Users/.../script.sh → /c/Users/.../script.sh under win32, plus the containment-unchanged assertion) are easy to port over — happy to open a tests-only follow-up against #23405's branch if @CalmProton wants them.