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/media/preview.js

@@ -0,0 +1,91 @@
+// Webview side of the YAPF preview: decode, draw, zoom, mip picker, info.
+(function () {
+  const vscode = typeof acquireVsCodeApi === 'function' ? acquireVsCodeApi() : null;
+  const canvas = document.getElementById('canvas');
+  const info = document.getElementById('info');
+  const controls = document.getElementById('controls');
+  const errorBox = document.getElementById('error');
+  const GPU_NAMES = ['RGBA8', 'RGB8', 'RG8', 'R8', 'SRGB8_A8', 'SRGB8'];
+  const CH_NAMES = ['', 'Gray', 'Gray + Alpha', 'RGB', 'RGBA'];
+
+  let image = null, level = 0, fit = true, zoom = 1;
+
+  function kb(n) { return n < 1024 * 1024 ? (n / 1024).toFixed(1) + ' KB' : (n / 1048576).toFixed(2) + ' MB'; }
+
+  function draw() {
+    const w = Math.max(1, image.width >>> level), h = Math.max(1, image.height >>> level);
+    canvas.width = w; canvas.height = h;
+    canvas.getContext('2d').putImageData(new ImageData(YAPF.toRGBA(image, level), w, h), 0, 0);
+    layout();
+  }
+
+  function layout() {
+    if (!image) return;
+    const w = canvas.width, h = canvas.height;
+    const stage = document.getElementById('stage');
+    const scale = fit ? Math.min(1, (stage.clientWidth - 32) / w, (stage.clientHeight - 32) / h) : zoom;
+    canvas.style.width = Math.max(1, Math.round(w * scale)) + 'px';
+    canvas.style.height = Math.max(1, Math.round(h * scale)) + 'px';
+    canvas.classList.toggle('pixelated', scale >= 2);
+    document.body.classList.toggle('fit', fit);
+    stage.title = fit ? 'Click for 100%, Ctrl+scroll to zoom' : 'Click to fit';
+  }
+
+  function show(name, bytes) {
+    errorBox.hidden = true;
+    const t = performance.now();
+    try {
+      image = YAPF.decode(bytes);
+    } catch (e) {
+      image = null;
+      errorBox.hidden = false;
+      errorBox.textContent = name + ': ' + e.message;
+      info.textContent = '';
+      return;
+    }
+    const ms = performance.now() - t;
+    const raw = image.width * image.height * image.channels;
+    level = Math.min(level, image.mipLevels - 1);
+    info.textContent = [
+      image.width + ' × ' + image.height,
+      CH_NAMES[image.channels],
+      (image.flags & 2 ? 'sRGB' : 'linear') + (image.flags & 1 ? ', premultiplied' : ''),
+      'GPU ' + (GPU_NAMES[image.gpuFormat] || '?'),
+      kb(bytes.length) + ' (' + (100 * bytes.length / raw).toFixed(1) + '% of raw)',
+      'decoded in ' + ms.toFixed(1) + ' ms',
+    ].join('  ·  ');
+
+    controls.textContent = '';
+    if (image.mipLevels > 1) {
+      const sel = document.createElement('select');
+      for (let m = 0; m < image.mipLevels; m++) {
+        const o = document.createElement('option');
+        o.value = m;
+        o.textContent = 'Mip ' + m + ' (' + Math.max(1, image.width >>> m) + '×' + Math.max(1, image.height >>> m) + ')';
+        sel.appendChild(o);
+      }
+      sel.value = level;
+      sel.onchange = () => { level = +sel.value; draw(); };
+      controls.appendChild(sel);
+    }
+    draw();
+  }
+
+  document.getElementById('stage').addEventListener('click', () => { fit = !fit; zoom = 1; layout(); });
+  document.getElementById('stage').addEventListener('wheel', (e) => {
+    if (!e.ctrlKey || !image) return;
+    e.preventDefault();
+    fit = false;
+    zoom = Math.min(64, Math.max(1 / 64, zoom * (e.deltaY < 0 ? 1.25 : 0.8)));
+    layout();
+  }, { passive: false });
+  window.addEventListener('resize', layout);
+
+  window.addEventListener('message', (e) => {
+    const m = e.data;
+    if (m.type === 'file') show(m.name, m.bytes instanceof Uint8Array ? m.bytes : new Uint8Array(m.bytes));
+    if (m.type === 'error') { errorBox.hidden = false; errorBox.textContent = m.message; }
+  });
+  if (vscode) vscode.postMessage({ type: 'ready' });
+  window.yapfPreviewShow = show;   // used by the browser test page
+})();