coaxmetal/hermes: add claude-code to agent PATH for claude-code skill
The Hermes Agent ships a "claude-code" skill that delegates coding via
`terminal(command="claude -p '...'")`, but the `claude` binary wasn't on
the agent's PATH. Add it through services.hermes-agent.extraPackages, which
lands in both the systemd service PATH and the hermes user's profile.
Auth is separate: run `sudo -u hermes -H claude` on the host once.
Assisted-by: Claude Code (claude-opus-4-8[1m])