JXL: patches at effort 2

Text-like features of screenshot-like areas (small components on flat
backgrounds that repeat) are found like libjxl's FindTextLikePatches, packed
into a reference frame (Modular, XYB quantized for the distance like libjxl's
Modular frames, gradient predictor), subtracted from the planes as they
decode, and added back by the frame's patch dictionary (kAdd). At effort 2
only, like cjxl -e 7: a page of text shrinks by 62%, screenshots by 1-2%.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Lfv41PqHEGbU7SLg5onpG1

Author: matmen

CHANGELOG.md

@@ -21,6 +21,10 @@
   its other tests that have text; the others need variable fonts (14), resvg's default font size of 12 pixels (instead
   of 16), its cursive and fantasy fonts, or render as resvg doesn't (in ways browsers don't either, like conjuncts
   broken at a font change).
+- `encodeJXL({ quality, effort: 2 })` stores text-like features that repeat (glyphs on the flat backgrounds of
+  screenshots) once, in a reference frame, and adds them where they occur, like libjxl's patches (`cjxl -e 7`, ported
+  from it): a page of text takes 62% fewer bytes (143x91 pixels: 1698 instead of 4458), screenshots 1-2% fewer, like
+  with cjxl. Images without such features stay as they are; finding them takes about 0.3 s per megapixel.
 - Decoding converts images with embedded ICC color profiles to sRGB, like browsers show them (`DecodeOptions.applyColorProfile`,
   default `true`, also for `Animation.decode()`): PNGs (iCCP, unless an sRGB chunk is there too), JPEGs (APP2), WebPs
   (ICCP, also animated), AVIFs (colr prof/rICC, which then describe the RGB values instead of the nclx box) and TIFFs.

THIRD_PARTY_NOTICES.md

@@ -17,7 +17,7 @@ following projects, under their own licenses. Each derived file says so in its h
 | [libaom](https://aomedia.googlesource.com/aom/) by the Alliance for Open Media | `src/codecs/av1/msac-enc.ts` (the symbol encoder), `src/codecs/av1/fdct.ts` (the forward Walsh-Hadamard transform), `src/codecs/av1/encode.ts` (the loop filter level from the quantizer), `src/codecs/avif-enc.ts` (the quantizer to qindex table) | BSD-2-Clause |
 | [libavif](https://github.com/AOMediaCodec/libavif) by Joe Drago | `src/codecs/avif.ts` (YUV to RGB conversion with bilinear chroma upsampling, alpha range expansion and unpremultiplication) | BSD-2-Clause |
 | [jxl-oxide](https://github.com/tirr-c/jxl-oxide) by Wonwoo Choi | `src/codecs/jxl/*` (the JPEG XL decoder: bit reader, header and frame header fields, entropy decoding, VarDCT, dequantization matrices, transforms, restoration filters, upsampling, the parsing of patches, splines and noise) | MIT (or Apache-2.0) |
-| [libjxl](https://github.com/libjxl/libjxl) by the JPEG XL Project Authors | `src/codecs/jxl/modular.ts` (Modular decoding: MA trees, predictors, the self-correcting predictor, transforms), `src/codecs/jxl/frame.ts` (the sections of frames, the order of the rendering stages, reference frames), `src/codecs/jxl/blend.ts`, `src/codecs/jxl/color.ts` (XYB to RGB), `src/codecs/jxl/features.ts` (rendering patches, splines and noise), `src/codecs/jxl/fast-lossless.ts` (the lossless encoder: palette detection, YCoCg, the gradient predictor, prefix codes, runs as LZ77, the headers) | BSD-3-Clause |
+| [libjxl](https://github.com/libjxl/libjxl) by the JPEG XL Project Authors | `src/codecs/jxl/modular.ts` (Modular decoding: MA trees, predictors, the self-correcting predictor, transforms), `src/codecs/jxl/frame.ts` (the sections of frames, the order of the rendering stages, reference frames), `src/codecs/jxl/blend.ts`, `src/codecs/jxl/color.ts` (XYB to RGB), `src/codecs/jxl/features.ts` (rendering patches, splines and noise), `src/codecs/jxl/fast-lossless.ts` (the lossless encoder: palette detection, YCoCg, the gradient predictor, prefix codes, runs as LZ77, the headers), `src/codecs/jxl/patches-enc.ts` (finding text-like patches, packing them into a reference frame, quantizing it like Modular XYB, the patch dictionary) | BSD-3-Clause |
 | [JPEG XL conformance](https://github.com/libjxl/conformance) by the JPEG XL Project Authors | `tests/jxl/alpha-*.jxl`, `animation-spline.jxl`, `blendmodes.jxl`, `mul-no-extra-channels.jxl` (test files) | BSD-3-Clause |
 | [Various smartphones - Android, Blackberry, Windows Phone, and iOS.jpg](https://commons.wikimedia.org/wiki/File:Various_smartphones_-_Android,_Blackberry,_Windows_Phone,_and_iOS.jpg) by Carlos Varela | `tests/targets/external.png` and `external.jpg` (a square of it, scaled to 638x638), the test files made from them (`tests/avif`, `tests/jxl`, `tests/ico`, `tests/hdr`, `tests/qoi`, `tests/tiffs`) and the test targets showing them; `bench/inputs/photo.jpg` (unmodified) | [CC BY 2.0](https://creativecommons.org/licenses/by/2.0/) |
 | [FreeType](https://freetype.org) | `src/render/hinting.ts` (behavior and parts of the logic of the TrueType interpreter) | FreeType License |