Every clone ran `git --version` first so an image without git could be
told so. The probe was one extra round trip that could not stop the
clone from failing a moment later for the same reason, and it covered
only the clone: a later status or push in an empty workspace failed
unexplained. The driver now classifies exit 127 and 126 from any git
command as `GitFailureKind::GitUnavailable`, so the clone reads the
class off its own failure and names the image requirement, and the
retry table treats the class as permanent.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>