YAPF v1: fast byte-aligned format, SIMD, tools and plugins

Format (version 1, replaces the earlier experimental versions):
- per-tile YCoCg-R or subtract-green colour transform, 8-bit modular
- 12 row filters per 8-row band (Left, Gradient, Up-right, Up-average,
  Up 1-8 rows), none with more than a one-add serial dependency
- residuals in groups of 8 at the group's width (w bits x 8 = w bytes),
  4-bit control codes with repeat-previous-width runs chosen by DP
- constant and stored tiles, independent 64x64 tiles, mips, GPU hints
- all sizes validated before decoding; corrupt input is rejected

Library:
- SIMD on by default: SSSE3 (runtime CPUID check; GCC, Clang, MSVC,
  MinGW) and NEON on ARM64; -DYAPF_NO_SIMD for plain C
- yapf_load_memory, yapf_load_mt, yapf_load_memory_mt
- 6-10x faster decoding than PNG (stb_image) on one core; -O2 and -O3
  builds perform the same
- fixes for macOS (sysconf) and the Windows import library exports

Tools and integrations:
- `yapf` CLI: convert PNG/JPG/TGA/BMP/PSD/GIF <-> YAPF, info, bench,
  thumbnail, mips
- JavaScript and Python bindings (byte-identical to the C encoder)
- GIMP 3 plugin: exports the flattened image, optional mipmaps
- Blender extension: import (also as plane), export, drag and drop
- VS Code preview, Figma plugin, Photoshop scripts, Linux MIME type and
  thumbnailer
- Makefile, updated build.sh / build.bat, tools/build_release.sh
- tests/test_yapf.c (784 checks) and bindings/js/test.js

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

extensions/blender/README.md

@@ -0,0 +1,34 @@
+# YAPF for Blender
+
+Import and export `.yapf` images in **Blender 4.2 or later** (tested with
+Blender 5.1).
+
+- **File → Import → YAPF Image (.yapf)** — optionally as a **plane** with a
+  material that shows the image.
+- **Image Editor → Image → Open YAPF… / Save as YAPF…** (with mipmaps option).
+- **Drag and drop** `.yapf` files into the 3D Viewport (creates a plane), the
+  Image Editor or a node editor.
+
+Blender cannot read `.yapf` on its own, so imported images are **packed into
+the .blend** and survive saving and reopening.
+
+## Install
+
+1. Get `yapf_image-blender.zip` from the
+   [Releases](https://github.com/Nexoniarz/YAPF/releases), or build it (below).
+2. Blender → **Edit → Preferences → Get Extensions → ⌄ → Install from Disk…**
+   and pick the zip.
+
+The zip contains the native YAPF library for Windows, macOS and Linux (x64
+and ARM64).  If no library matches your system, the extension still
+**imports** using a pure-Python decoder (numpy, bundled with Blender), but
+cannot export.
+
+## Build the zip
+
+```sh
+python3 extensions/blender/build.py            # library for this machine only
+tools/build_release.sh                         # all platforms (needs zig)
+```
+
+Both write `dist/yapf_image-blender.zip`.