Guidance for nlsh remote mode (--remote flag). Use when commands execute on
a remote server via SSH tunnel. Teaches: (1) Commands run on REMOTE not local,
(2) Use upload_file for local-to-remote file transfers (not scp/rsync),
(3) Use download_file for remote-to-local transfers, (4) Local env vars like
NLSH_REMOTE_HOST are unavailable on remote.