[Request] Merge apk architecture picker flag

For example, the size of **org.mozilla.firefox_beta_151.0b1.apkm** is 270MB. And after merged is 560MB
So, add a flag to pick only the wanted architecture to reduce file size and return an error if that architecture does not exist.

<img width="961" height="504" alt="Image" src="https://github.com/user-attachments/assets/5f571f34-3e4d-4239-b8c6-f588cd729343" />