Reqly HEIC decoder source and replacement instructions

Distributed decoder: libheif-js 1.23.2 (LGPL-3.0), with libheif at
ac1cb05c39008f01525c991ff8b88f84ddf70fd2 and libde265 1.0.15.
Build provenance: catdad-experiments/libheif-emscripten tag v1.23.2.
Its workflow uses Emscripten 3.1.61 and disables unsafe JS evaluation.
The unmodified upstream sources and build scripts are supplied beside this file:
/sources/libheif-js-1.23.2.tar.gz
/sources/libheif-emscripten-1.23.2.tar.gz
/sources/libheif-ac1cb05.tar.gz
/sources/libde265-1.0.15.tar.gz
/sources/reqly-heic-integration.tar.gz
License texts: /licenses/libheif-js-LGPL-3.0.txt, /licenses/GPL-3.0.txt,
/licenses/libheif.txt, /licenses/libde265.txt, /licenses/emscripten.txt.

Upstream URLs:
https://github.com/catdad-experiments/libheif-js/tree/1.23.2
https://github.com/catdad-experiments/libheif-emscripten/tree/v1.23.2
https://github.com/strukturag/libheif/tree/ac1cb05c39008f01525c991ff8b88f84ddf70fd2
https://github.com/strukturag/libde265/tree/v1.0.15

Rebuild the upstream decoder using the workflow/build scripts in those sources.
For the browser variant, use USE_WASM=1 USE_UNSAFE_EVAL=0 and the pinned
Emscripten toolchain. The libheif-js scripts/install.js accepts a locally built
libheif-emscripten distribution tarball and produces the bundled ES module.

To relink Reqly's integration with a replacement decoder:
1. Extract reqly-heic-integration.tar.gz into a new directory.
2. Run npm ci (requires Node satisfying the package engines).
3. Replace node_modules/libheif-js/libheif-wasm/libheif-bundle.mjs with your
   compatible rebuilt module; preserve the factory interface used by src/types.
4. Run node scripts/rebuild-heic.mjs.
5. In your static site copy, replace the existing _astro/heic.worker-*.js file
   contents with rebuilt-heic/heic.worker.js, retaining its existing filename.
6. Serve locally, clear the browser cache, and rerun image conversion checks.

Reqly does not prohibit reverse engineering or modification for debugging
changes to these LGPL libraries. Source is provided for inspection and relinking;
this notice does not claim ownership of or change the upstream licenses.
The library is supplied without warranty, as stated in its license.

Test fixture rainbow.heic is from the pinned libheif tests/data source tree.
It is used only in development and is not part of the deployed image tools.