Testlab instance requirements

config-weave test shells out to the sibling vmlab CLI for every instance, so vmlab and KVM are the only host requirements — there is no container runtime to install.

Instance	Requirement
container (image)	an OCI image with a shell; pulled by vmlab, run in a micro-VM
vm (template)	the template must ship the vmlab guest agent; each group gets a throwaway one-VM lab
vm (Windows)	guests must be Server 2019 / Windows 10 or newer