rusty_jpeg 0.2.3

Pure-Rust JPEG/MJPEG decoder + encoder, no C/FFI. Baseline and progressive DCT, planar YUV in/out, AVX2 FDCT/quantize and a two-block AVX2 IDCT. Box-averaged chroma, opt-in trellis, fuzz-tested. Encodes 1.22x faster than FFmpeg at matched output size; decodes ~1.04x faster.