fix(ssh): support macOS tar during file sync

[verybigdog]

Summary

• Detect whether the remote tar supports GNU --no-overwrite-dir before SSH bulk uploads
• Fall back to macOS/bsdtar-compatible extraction with tar xmf - -C /
• Add regression tests for GNU tar vs bsdtar command selection

Test Plan

• python -m pytest tests/tools/test_ssh_environment.py -q

Context

SSH workers targeting macOS currently hit a persistent file-sync warning because macOS ships bsdtar, which rejects GNU tar's --no-overwrite-dir. The fallback keeps GNU tar's safer behavior where available while allowing macOS SSH environments to sync cleanly.

[verybigdog]

Closed by author request: this change was opened against the upstream repository by mistake. We will route it through the maintained downstream/fork workflow instead.