generate_launchd_plist() and generate_systemd_unit() were missing the
--profile <name> argument in ProgramArguments/ExecStart, causing
hermes gateway start to regenerate plists that fell back to
~/.hermes/active_profile instead of the intended profile.
Fix:
- Add _profile_arg(hermes_home?) helper returning '--profile <name>'
only for ~/.hermes/profiles/<name> paths, empty string otherwise.
- Update generate_launchd_plist() to build ProgramArguments array
dynamically with --profile when applicable.
- Update generate_systemd_unit() both user and system service
branches with {profile_arg} in ExecStart.
This ensures hermes --profile <name> gateway start produces a
service definition that correctly scopes to the named profile.