LR-IMP-FORMATS: decode Nikon "lossy after split" NEF

Rows below the split row use the existing lossy Huffman path; from the split
row on every pixel is a (bits - 4)-bit word: a complete prefix code for the
difference category followed by the top bits of the T.81 extra bits, dequantised
to the centre of the kept bin, with the usual two-left predictor and an
unclamped running value. The rule was derived by black-box analysis of the 11
CC0 samples (all decode to the same samples as the analysis decoder).

The decoder checks that the fixed-rate section ends within the last byte of the
strip (whole rows plus 0..7 padding bits) and otherwise keeps refusing the file
(preview only), so a file that does not follow the rule is never decoded wrongly.

RENDER_CACHE_VERSION 28 (main is 22, open PRs use 23-27): adjust at merge.

crates/engine/src/media.rs

@@ -62,7 +62,7 @@ impl SettingsHashes {
 }
 
 /// Bump when the pipeline's output changes, to invalidate cached thumbnails.
-pub const RENDER_CACHE_VERSION: u64 = 22;
+pub const RENDER_CACHE_VERSION: u64 = 28;
 
 /// Thumbnails render at one of these long edges (so window/cell size changes reuse the cache).
 pub const THUMB_SIZES: [usize; 4] = [128, 256, 384, 512];