Add CommunicationService.RefreshDeploymentAsync — the typed send method
for the small notify-and-fetch wire message (RefreshDeploymentCommand).
Mirrors DeployInstanceAsync exactly: SiteEnvelope + Ask<DeploymentStatusResponse>
bounded by DeploymentTimeout. CentralCommunicationActor needs no change
(HandleSiteEnvelope is fully generic — all SiteEnvelope messages forward
to /user/site-communication without a per-type switch). Adds a parallel
routing test asserting the envelope reaches the site ClusterClient.
Joseph Doherty
25f768f379