Summary

When the launchd plist file is missing (manual cleanup, failed upgrade, launchd state drift), hermes gateway start now regenerates the plist, loads it, and starts the service instead of crashing with exit status 3.

Problem

Previously, refresh_launchd_plist_if_needed() returned early if the plist was missing:

if not plist_path.exists() or launchd_plist_is_current():
    return False

And the recovery path in launchd_start() was skipped because it only triggered when the plist existed:

if e.returncode != 3 or not plist_path.exists():
    raise

This meant users in the missing-plist state had to run hermes gateway install manually to recover.

Solution

Check for missing plist at the start of launchd_start() and self-heal:

1. Regenerate the plist
2. Load it with launchctl load
3. Start the service

This makes hermes gateway start robust to missing plists, regardless of how the plist disappeared.

Testing

Added regression test: test_launchd_start_recreates_missing_plist_and_loads_service

Fixes #3318