fix(train-scheduling): exempt direct-to-train export bookings from GRN gate

confirmScheduleLoading's assertExportBookingsReceived checked every
wagon-assigned export booking for a warehouse GRN, with no exception for
DIRECT_TO_TRAIN (manual truck-straight-to-wagon) bookings — the one
call site that lacked the carve-out already applied everywhere else GRN
is checked (export-received-gate, booking-journey, carriage acceptance).
Warehouse-routed export cargo still requires GRN; direct handovers rely
on the carriage acceptance sheet instead.

apps/edr-freight-api/src/modules/train-scheduling/services/train-scheduling.service.ts

@@ -3262,6 +3262,12 @@ export class TrainSchedulingService {
    * Every export booking being confirmed loaded must already be received at the
    * warehouse with a GRN. An allocation puts a booking on a wagon on paper; this
    * is the check that the cargo is physically in the yard before we call it loaded.
+   *
+   * Direct truck-to-train (exportHandoverMode = DIRECT_TO_TRAIN) is excluded —
+   * that cargo is manually loaded from the customer's truck straight onto the
+   * wagon, never sees the warehouse, and is never GRN'd. Its custody is attested
+   * by the carriage acceptance sheet instead (same carve-out as the shared
+   * assertExportReceivedWithGrn gate — see common/export-received-gate.ts).
    */
   private async assertExportBookingsReceived(bookingIds: string[]): Promise<void> {
     if (!bookingIds.length) return;
@@ -3270,6 +3276,7 @@ export class TrainSchedulingService {
          FROM freight.bookings b
         WHERE b.id = ANY($1)
           AND b.deleted_at IS NULL
+          AND b.export_handover_mode IS DISTINCT FROM 'DIRECT_TO_TRAIN'
           AND NOT EXISTS (
             SELECT 1 FROM freight.warehouse_inventory inv
              WHERE inv.booking_id = b.id