Add passwordless ssh setup back

[lukemartinlogan]

Passwordless SSH (multi-node convenience)

For clouds/bare-metal (e.g., Chameleon, CloudLab), set up SSH keys across nodes.

1. Copy your key to a seed node (example IP):

jarvis ssh copy ~/.ssh/id_ed25519 129.127.0.124

2. Set your hostfile with all target nodes:

jarvis hostfile set ~/hostfile.txt

3. Distribute the key to all nodes:

jarvis ssh distribute ~/.ssh/id_ed25519