Function current_rollout_ids 

pub fn current_rollout_ids(
    fleet: &FleetResolved,
    fleet_resolved_hash: &str,
) -> HashSet<String>

RolloutIds the current fleet snapshot expects across all channels. Filters host_dispatch_state snapshots to “this rev’s rollouts only” so stale Converged rollouts from a previous rev don’t poison gate evaluation. Consumed by polling, the deferrals route, and the per-checkin dispatch pipeline; centralising it keeps the filter consistent. Errored channels are silently dropped (callers log at their site, this fn stays pure).