Fixes#898 — Python 3.11 changed argparse to raise an exception on
duplicate subparser names (CPython #94331). The 'skills' name was
registered twice: once for Skills Hub and once for skills config.
Changes:
- Remove duplicate 'skills' subparser registration
- Add 'config' as a sub-action under the existing 'hermes skills' command
- Route 'hermes skills config' to skills_config module
- Add regression test to catch future duplicates
Migration: 'hermes skills' (config) is now 'hermes skills config'