Function record_dlq 

pub fn record_dlq(
    db_path: &Path,
    sub_id: &str,
    correlation_id: &str,
    event_type: &str,
    payload: &str,
    retry_count: i64,
    last_error: &str,
    first_failed_at: &str,
    last_failed_at: &str,
) -> Result<()>

v0.7.0 K6 — append a subscription_dlq row for a delivery that exhausted the [200ms, 1s, 5s] retry ladder. K7’s inspector tool surfaces these rows to operators; K6 only ships the writer.