ghostscript writes PNG files we can't decode

``` ~/Downloads/ghostscript-10.05.1/bin/gs -sDEVICE=fpng -sOutputFile=bitmap.png -dBATCH -dNOPAUSE jbig2-pdfs/bitmap.pdf ``` This produces this file: <img width="399" height="400" alt="Image" src="https://github.com/user-attachments/assets/b417bcf6-ae93-4204-8282-e3ef71b774fe" /> But: ``` % Build/lagom/bin/image -o out.webp bitmap.png Runtime error: Reached end-of-stream without collecting the required number of bits ```