Control Plane Mesh connector

> opening new issue for
>
> Possibly related, and happy to file separately if confirmed: NewServer installs NewNopMeshAdapter() (internal/controlplane/server.go), whose PublishEvent does not publish (internal/controlplane/mesh.go), and cmd/sam-control-plane/main.go never replaces it. Rotation/revocation events look implemented and handled node-side, but not propagated by the shipped control-plane binary. The tests that exercise propagation call SetMeshAdapter themselves.
>

_Originally posted by @aojea in [#296](https://github.com/google/sam/issues/296#issuecomment-5424227038)_

This is still missing

Start with internal/controlplane/server.go and internal/controlplane/mesh.go, then inspect cmd/sam-control-plane/main.go to trace how NewServer installs its mesh adapter. Run the existing propagation tests that call SetMeshAdapter and compare that setup with the shipped binary. Done means rotation and revocation events propagate through the control-plane binary without test-only adapter configuration.

Written by the indexing model from the issue text.