Adds `cached-call retry` and `cached-call discard` subcommands that relay
to the existing Deployer-gated RetryParkedMessageCommand /
DiscardParkedMessageCommand via the central SiteCallAuditActor → site relay.
ManagementCommandRegistry already covered both types via reflection auto-discovery.
CommandTreeTests updated to include cached-call (group count 16 → 17).
Joseph Doherty