The Moon+ Reader import flow asks for .mrexpt files via the 'generic'
preset. On Android, Tauri routes that to the Storage Access Framework
picker, which filters by MIME type. Extensions without a registered MIME
(such as .mrexpt) end up greyed-out and unselectable.
Books and dictionaries already bypass this by using an unfiltered picker
and re-applying the extension whitelist client-side. Extend the same
treatment to the 'generic' preset so callers can request arbitrary
extensions reliably on Android. iOS already had no SAF restriction.
loveheaven
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