Reconciliation cursor becomes composite (UpdatedAtUtc, TrackedOperationId);
IPullSiteCallsClient/GrpcPullSiteCallsClient forward the Task-15 after_id keyset
(additive param, null preserves the legacy inclusive >= contract). A burst
sharing one exact UpdatedAtUtc now drains via the id tiebreak instead of pinning
forever. A legacy site that ignores after_id is latched + published as
SiteCallReconciliationPinnedChanged on the EventStream (transition-only),
replacing the prior silent log line.
Joseph Doherty