Function attach_journal_subscriber_tail 

pub fn attach_journal_subscriber_tail(
    opts: &AttachOptions,
    lane: &str,
) -> Result<ShmJournalSubscriber, BackingError>

Attach to a journal subscriber starting at the current tail (safe-by-default).

This avoids unintentionally replaying old data unless an operator explicitly requests it via attach_journal_subscriber_from.