docs: add Open Graph social preview image to guide page

- og-image.png from hero screenshot (522 KB)
- og:title, og:description, og:image meta tags
- twitter:card summary_large_image for Twitter/X previews
- Updated pages workflow to copy og-image.png

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: unamedkr

.github/workflows/pages.yml

@@ -41,6 +41,7 @@ jobs:
           cp wasm/_headers _site/_headers 2>/dev/null || true
           # Educational guide (/guide)
           cp site/index.html _site/guide/ 2>/dev/null || true
+          cp site/og-image.png _site/guide/ 2>/dev/null || true
 
       - name: Setup Pages
         uses: actions/configure-pages@v5

site/index.html

@@ -5,6 +5,16 @@
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>quant.cpp — Understanding KV Cache Compression</title>
 <meta name="description" content="An educational guide to KV cache compression in LLM inference. Learn how quant.cpp achieves 6.4x compression with only 3% quality loss.">
+<!-- Open Graph / Social Preview -->
+<meta property="og:title" content="quant.cpp — AI's Memory, Compressed 6.4x">
+<meta property="og:description" content="An interactive guide to KV cache compression. 4 orthogonal techniques achieve 6.4x compression at 3% quality cost.">
+<meta property="og:image" content="https://quantumaikr.github.io/quant.cpp/guide/og-image.png">
+<meta property="og:url" content="https://quantumaikr.github.io/quant.cpp/guide/">
+<meta property="og:type" content="website">
+<meta name="twitter:card" content="summary_large_image">
+<meta name="twitter:title" content="quant.cpp — AI's Memory, Compressed 6.4x">
+<meta name="twitter:description" content="An interactive guide to KV cache compression. 6.4x compression, 59% faster attention, 3% quality cost.">
+<meta name="twitter:image" content="https://quantumaikr.github.io/quant.cpp/guide/og-image.png">
 <style>
 /* ===== Reset & Base ===== */
 *{margin:0;padding:0;box-sizing:border-box}