test(mdm): verify launcher retry semantics with a fake binary

A fake git-ai that fails twice then hands off to the real binary must end in
a healthy daemon after exactly three attempts; one that always fails must
leave the login mechanism (launchd job, systemd unit, scheduled task)
reporting failure after five attempts with no daemon running.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>