Some PDFs may require the default app

What changed

PDF previews now use bounded range reads instead of copying the entire file into the app. PDFs that require a single contiguous range larger than 16 MiB show an option to open with the system default app.

Why this matters to the user

Large PDFs can preview with lower memory pressure when each requested range stays within the safety cap, regardless of total file size. A PDF containing an unusually large individual data stream may no longer preview inline even when the file itself is smaller than 50 MiB.

What the user should do

Use Open with default app when Cherry Studio reports that part of the PDF is too large to preview safely.

Notes for release manager

The 16 MiB boundary applies to one contiguous pdf.js range, not to the total PDF size. Removing it safely requires a local transport that can stream range bodies without assembling them in the renderer.