added instruction

src/Form/CollectionHarvestForm.php

@@ -136,6 +136,8 @@ final class CollectionHarvestForm extends FormBase {
         $collections[$node->id()] = $node->label();
       }
     }
+    asort($collections);
+    $form_state->set('collections', $collections);
 
     // Load media use taxonomy terms.
     $vid = 'islandora_media_use';
@@ -146,6 +148,11 @@ final class CollectionHarvestForm extends FormBase {
       $media_use_options[$term->tid] = $term->name;
     }
 
+    $form['introduction'] = [
+      '#type' => 'markup',
+      '#markup' => '<p><strong>' . $this->t("Select collection  and media use to harvest.  A zip of the media files will download to your computer.") . '</strong></p>',
+    ];
+
     // Collection selector.
     $form['collection'] = [
       '#type' => 'select',
@@ -225,12 +232,14 @@ final class CollectionHarvestForm extends FormBase {
 
     // Store only IDs for serialization safety.
     $temp_store = $this->tempStoreFactory->get('islandora_collection_harvest');
-    $zip_filename = 'collection_' . time() . '.zip';
+    $collections = $form_state->get('collections');
+    $collection_id = $form_state->getValue('collection');
+    $collection_label = $collections[$collection_id] ?? 'collection';
+    $sanitized_name = preg_replace('/[^a-z0-9_\-]+/i', '_', $collection_label);
+    $zip_filename = $sanitized_name . '_' . time() . '.zip';
+
     $temp_store->set($zip_filename, array_map(fn($m) => $m->id(), $media_entities));
 
-    // Notify the user and redirect to download.
-    $this->messenger()
-      ->addStatus($this->t('Your ZIP download has been initiated. Please wait for it to start.'));
     $form_state->setRedirect('islandora_collection_harvest.download_zip', ['filename' => $zip_filename]);
   }