Function prune_snapshots 

pub fn prune_snapshots(
    snapshots_dir: &Path,
    channel: &str,
) -> Result<usize, SnapshotError>

Delete oldest snapshots for channel until at most MAX_SNAPSHOTS_PER_CHANNEL remain. Returns the number pruned. Pruning errors on a specific entry are logged and skipped rather than aborting the whole sweep (one bad dir shouldn’t keep storage growing).