Floating-Point JPEG Decoder

This repo rips out STB-Image's fixed-point iDCT and 8-bit pipeline and replaces it with a float32 path so YUV->RGB conversion and resampling keep extra precision — you can actually see less banding in the provided GIFs and histograms. It also supports encoding float pixels back to JPEG and ships demos that explore recompression stability, which is a neat, very focused trick if you only have JPEGs (RAW still wins).