Replaces the abandoned PSWSMan approach (New-PSSession hangs on Linux)
with a Python-native implementation using the proven pypsrp WinRmTransport.
- New `template prepare-win` command in commands/template.py: starts VM,
waits for WinRM, uploads and runs Install-CIToolchain-*.ps1, handles
Windows Update 3010 reboot loop (max 10 iterations), installs CI-StaticIp
scheduled task, runs post-setup validation, graceful shutdown, snapshot.
- Helpers: _ps_escape, _wait_tcp, _parse_exit_marker, _wait_winrm.
- 40 new tests in test_commands_template.py covering all major branches.
- Fix test_commands_job.py: patch load_config in _patch_common so tests
don't pick up live /var/lib/ci/config.toml ip_pool and fail on lock.
- Coverage gate: 90.06% (was 88.95% before fix).