CI: add rollout baseline

[ohmyfelix]

What changed

• Add a Test job before the reusable Docker Build job with SSH, sshpass, and shell smoke checks.
• Add Docker Hub description publishing as a Docs job for dockette/ssh.
• Normalize Makefile build, test, and run targets.
• Normalize README badges to the dockette/copybara style and keep the standard Maintenance section.

Why

• Brings dockette/ssh onto the Dockette CI rollout baseline with lightweight image validation and Docker Hub docs publishing.