🌱 Create Host Yaml

[guettli]

Summary

This PR adds a new create-host-yaml command and updates the existing CLI ergonomics around host validation.

Changes

add sub-command caphcli create-host-yaml SERVER_ID OUTPUT_FILE:

• connect to Hetzner Robot, reboot the server into rescue, inspect disks, and write a HetznerBareMetalHost YAML file
• include all discovered WWNs in the generated YAML while leaving exactly one WWN uncommented
• select the active WWN from the smallest disk larger than 1 GB, breaking ties by WWN

change caphcli check-bm-servers to take the YAML file as a positional argument instead of --file

update generated CLI help and README examples