feat(latest): record one poll pass per exit with skip reason and outcome counts

Every way a Lane pass can end now writes exactly one durable row: a skip
value naming the exit (paused, refusing, sidecar-down, no-fetcher,
due-query, asleep, eligible-count, nothing-eligible, or empty for the
loop), five outcome counts from the classification the Series read already
makes, and carry-forward of the previous pass's figures exactly when the
pass's own gap is zero. Refusal is durable through the poll_lanes row, so
a restart does not re-probe a Site inside its backoff. Retention is 14
days. The mid-loop browser-unreachable return writes an empty skip by
design: a tenth value is not invented here. (#141)

backend/internal/store/store.go

@@ -1140,18 +1140,20 @@ func (s *Store) PausedLanes() ([]LanePause, error) {
 	return out, rows.Err()
 }
 
-// LanePausedUntil reads a Site's pause stamp. A missing state row is the
-// default unpaused state.
-func (s *Store) LanePausedUntil(site string) (int64, error) {
-	var until int64
-	err := s.db.QueryRow(`SELECT paused_until FROM poll_lanes WHERE site = $1`, site).Scan(&until)
+// LaneGates reads a Site's pause and refusal stamps in one row read — the
+// top-of-pass gate the poller uses (issue #141). A missing state row is the
+// default: unpaused and not refusing.
+func (s *Store) LaneGates(site string) (pausedUntil, refuseUntil int64, err error) {
+	err = s.db.QueryRow(
+		`SELECT paused_until, refuse_until FROM poll_lanes WHERE site = $1`, site).
+		Scan(&pausedUntil, &refuseUntil)
 	if errors.Is(err, sql.ErrNoRows) {
-		return 0, nil
+		return 0, 0, nil
 	}
 	if err != nil {
-		return 0, fmt.Errorf("lane pause %s: %w", site, err)
+		return 0, 0, fmt.Errorf("lane gates %s: %w", site, err)
 	}
-	return until, nil
+	return pausedUntil, refuseUntil, nil
 }
 
 // DueForLatestCheck returns one Site's series whose server-side