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/vscode/README.md

@@ -0,0 +1,27 @@
+# YAPF Image Preview for VS Code
+
+Click any `.yapf` file in VS Code to see the image.
+
+- Checkerboard behind transparent pixels.
+- **Click** to switch between *fit to window* and *100 %*; **Ctrl + scroll**
+  to zoom (pixels stay sharp when enlarged).
+- Picker for every **mip level** stored in the file.
+- Info bar: size, channels, sRGB / linear, GPU format hint, file size and
+  compression ratio, decode time.
+- Reloads automatically when the file changes on disk.
+
+Decoding runs in plain JavaScript inside the preview; no native code.
+
+## Install
+
+- From a release: download `yapf-preview.vsix`, then in VS Code run
+  **Extensions: Install from VSIX…** (or `code --install-extension yapf-preview.vsix`).
+- From source (needs Node.js):
+
+  ```sh
+  cd extensions/vscode
+  npm run package          # → yapf-preview-1.0.0.vsix
+  code --install-extension yapf-preview-1.0.0.vsix
+  ```
+
+Works in VS Code, VSCodium and other VS Code–based editors (1.75+).