Function mark_session_target_missing_if_current 

pub fn mark_session_target_missing_if_current(
    session_id: &str,
    detail: &str,
    updated_at: &str,
    observed_updated_at: &str,
) -> Result<Option<SessionState>>

Record a definitive worker failure only while the observed session record is still current. A delayed background write must not invalidate a resume.