Re-read a delivery before failing it for a missing target

failMissingTarget failed the delivery as the batch had read it, so a
delivery a worker sent and let go between the batch read and the
ownership check could end failed after a successful attempt. It now
reads the row once it owns the delivery and fails it only if the
status is still the one the batch read, as processNewTask does. A row
that cannot be read is left alone.

TestSweepPending_TargetDeleted now checks that the first sweep already
queues the healthy delivery and the second does not queue it again.

Model: opus-5-5

internal/delivery/export_test.go

@@ -321,6 +321,16 @@ func (e *Engine) ExportRecoverRetryingDeliveries(
 	e.recoverRetryingDeliveries(webhookDB, webhookID)
 }
 
+// ExportFailMissingTarget exposes failMissingTarget, so a test can hand
+// it a delivery as a batch read it earlier.
+func (e *Engine) ExportFailMissingTarget(
+	webhookDB *gorm.DB,
+	webhookID string,
+	d *database.Delivery,
+) {
+	e.failMissingTarget(webhookDB, webhookID, d)
+}
+
 // ExportDeliveryCh returns the delivery channel.
 func (e *Engine) ExportDeliveryCh() chan Task {
 	return e.deliveryCh