Get-PinnedGit no longer invokes tar at all (no $inboxTar seam exists since
the PortableGit pin), so the C# stub tar.exe and the Invoke-Native override
that bound it were never reached: the test compiled a stub for nothing and
its docstring described a mechanism the installer does not have. Keep the
real-download Get-PinnedGit run under a bzip2-less PATH and the git.exe +
bash.exe contract checks; that is what the test proves.