Route managed LaunchAgent package self-updates through the post-exit CLI handoff path and persist handoff helper failures through the update restart sentinel so agent-invoked updates cannot stay pending indefinitely.
Add handoff ownership guards for stale helpers, atomic helper sentinel writes, and regression coverage for unrelated and newer pending sentinels.
Fixes#81894.
Co-authored-by: B.K. <bandark@mac.com>
22a0ca9e3b