test: expand corpus tests to full source×format matrix, add HEIC and ICC profile tests

- All corpus-builder sources (PNG, JPEG, WebP, AVIF, JXL, GIF) now test
  against all 6 target formats (jpg, png, webp, jxl, avif, gif)
- Added animated corpus placeholders: avif-animated, jxl-animated
- Added WebP animated → png/jpg tests (first-frame extraction)
- Added GIF animated → png/jpg tests
- Added HEIC → all formats (png, jpg, webp, avif, jxl) from /mnt/v/heic/
- Added ICC profile tests from /mnt/v/datasets/non-srgb-by-profile/:
  adobe-rgb, display-p3, prophoto-rgb, rec-2020-pq, bt709, camera-rgb, grayscale
- Expanded wide-gamut and weird to all target formats
- Expanded repro-images to jpg/webp targets
- Fix zen_decoder.rs: ImageInfo.has_animation → ImageSequence::Animation match

Author: lilith

imageflow_core/src/codecs/zen_decoder.rs

@@ -757,7 +757,8 @@ impl Decoder for ZenDecoder {
         ];
 
         // Animation path: use persistent full-frame decoder
-        if self.meta.always_use_frame_decoder || info.has_animation || self.frame_dec.is_some() {
+        let is_animated = matches!(info.sequence, zc::ImageSequence::Animation { .. });
+        if self.meta.always_use_frame_decoder || is_animated || self.frame_dec.is_some() {
             if self.frame_dec.is_none() {
                 let data = self.data.take().unwrap();
                 let target = self.target_frame;