Previously, `hermes gateway install --system` hard-refused to create a
service running as root, even when explicitly requested via
`--run-as-user root`. This forced LXC/container users (where root is
the only user) to either create throwaway users or comment out the check
in source.
Changes:
- Auto-detected root (no explicit --run-as-user) still raises, but with
a message explaining how to override
- Explicit `--run-as-user root` now allowed with a warning about
security implications
- Interactive setup wizard prompt accepts 'root' as a valid username
(warning comes from _system_service_identity downstream)
- Added tests for all three paths: auto-detected root rejection,
explicit root allowance, and normal non-root passthrough
23addf48d3