Update background assembly instructions for saved completion gates

docs/authoring/combining_interviews.md

@@ -327,7 +327,7 @@ Review the combined interview to ensure a smooth user experience.
 4. **Smoothing shared routing logic:** Adjust text and logic to gracefully handle the combined context. For example, if a child interview assumes the user is only generating that specific form, you may need to open up the choices so the user can dynamically decide to create the form using the interview, upload an existing one, or wait until later.
 5. **Handling large document packets:** Combined interviews often generate many documents. 
    - **Remove previews:** Remove document previews (e.g., `${ al_court_bundle.as_pdf(key='preview') }`) from signature screens. Generating a preview of a massive packet can be very slow or break the layout. Instead, use a simple confirmation message like *"Review your answers before you sign"*.
-   - **Use background assembly:** If your interview generates more than ~3 documents, you should switch to background processing to prevent the server from timing out. Update your final download screen to use `al_user_bundle.download_list_html(use_previously_cached_files=True, include_full_pdf=True)`. See the [background assembly documentation](../components/AssemblyLine/background_assembly.md) for more details.
+   - **Use background assembly:** If generating your combined packet is slow enough to risk a timeout, use background processing. After collecting all attachment inputs, reference `al_user_bundle.downloads_with_docx_ready` in your interview order before the download screen. On that screen, use `al_user_bundle.download_list_html(use_previously_cached_files=True, include_full_pdf=True)` to display the saved files. See the [background assembly documentation](../components/AssemblyLine/background_assembly.md) for more details.
 6. **Overriding attachment blocks:** Keep in mind that you can also override an attachment block (e.g., an `attachment:` block that generates a PDF) directly in the parent umbrella interview. Because Docassemble uses the last loaded block with a matching variable name, you aren't forced to make the included YAML totally reusable without changes. You can let the child interview define the base attachment block, and simply redefine it in your `main_` YAML if the combined context requires different formatting or logic.
 7. **Document integration points:** It is crucial for the author to document the integration points of the child (included) interview. Clearly explain in comments or an external `README` what specific variables need to be set—especially those that might not be standard AssemblyLine variables—for the child interview to work properly when included in a parent interview.
 8. **Test:** Run the main interview and verify that the sections flow logically, there are no missing variables, and progress bars or navigation menus behave smoothly.