stripping metadata of a `jxl` image breaks the image

Tested on 0213e7d7c47aefad9018618e275c4ab49cf988c2 ``` $ cargo run -- ~/Downloads/zoltan-tasi-CLJeQCr2F_A-unsplash.jxl -strip ~/Downloads/zoltan-tasi-CLJeQCr2F_A-unsplash.jxl ... Running `target/debug/wm-convert ~Downloads/zoltan-tasi-CLJeQCr2F_A-unsplash.jxl -strip ~/Downloads/zoltan-tasi-CLJeQCr2F_A-unsplash.jxl` wondermagick: no decode delegate for this image format `jxl' @ src/encode.rs/choose_encoding_format/101. ``` Actually, running `-strip` or `-identify` (of #30) doesn't make a difference, the image is never written out properly. <img width="550" height="61" alt="Image" src="https://github.com/user-attachments/assets/cb6e345f-aeb9-4c82-860a-114c1309948b" />