Allow next download to start while previous one is assembling

Checklist

• I'm reporting a feature request
• I've verified that I'm running xdm latest version
• I've searched the bugtracker for similar feature requests including closed ones

Description

WRITE DESCRIPTION HERE Hi, I really like using XDM, but there’s one thing that slows down batch downloads:

When a download finishes, XDM starts assembling the file, but it waits for that process to finish before starting the next file in the queue.

It would be much better if the next download could start while the previous one is assembling — like parallel handling of assembling and downloading.

This would improve efficiency for users who download many large files.

Please consider adding this as an option in future updates. Thank you!