Expression-bodied SetAction lambdas were binding to Func<ParseResult,Task>
and discarding the int returned by ExecuteCommandAsync, so the process always
exited 0 even on error/403. Switch both to block-body `return await` to select
the Task<int> overload, matching every sibling command group. Also collapse the
four duplicate static option fields (RetrySiteId/DiscardSiteId,
RetryMessageId/DiscardMessageId) to two shared fields (SiteIdOption,
MessageIdOption) — safe because retry and discard are sibling sub-commands.
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