LR-IMP-FORMATS: HEIC decodes like libheif; release builds include it

heic-rs reconstructs iPhone HEVC tiles bit-exactly (checked against libde265), but
its colour stage was 2-27 code values off libheif on every iPhone photo: it ignores
the HEVC VUI and assumes BT.709 limited range. lightcraft-heif now converts YCbCr
itself (nclx, else VUI, else H.265 defaults; nearest chroma, bilinear for odd clap
offsets, as libheif), inherits tile ICC/nclx on grids, follows libheif's imir axis
and clap rounding, and outputs 16-bit RGB. Measured on 30 real and synthetic
files: within 1 code value of libheif (pillow-heif 1.8 / libheif 1.23).

Also: HEIF header reader for import (no pixel decode), embedded thumbnail for small
decodes, nclx/VUI colour hint (shared CICP mapping with PNG), clear 4:2:2/4:4:4
Unsupported error, Format::not_decodable as the one source of "why not" (import
reports "HEIC/HEIF support isn't included in this build"), `.heif` imports.
Release packaging and Nix build with the heif feature, as whats-new promised.
lightcraft_heif::testdata writes lossless (PCM) synthetic HEICs for the tests.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packaging/linux/package.sh

@@ -42,7 +42,7 @@ BASENAME="lightcraft-$VERSION-linux-$ARCH"
 echo "==> LightCraft $VERSION for Linux $ARCH ($FORMATS)"
 
 if [ "$SKIP_BUILD" = 0 ]; then
-  (cd "$ROOT" && cargo build --release --locked -p lightcraft -p lightcraft-cli)
+  (cd "$ROOT" && cargo build --release --locked -p lightcraft -p lightcraft-cli --features lightcraft/heif,lightcraft-cli/heif)
 fi
 BIN="$CARGO_TARGET_DIR/release"
 WORK="$CARGO_TARGET_DIR/linux-package"