feat: educational guide site + deploy to GitHub Pages (/guide)

Interactive educational guide explaining KV cache compression:
- Chapter 1-6: Problem → KV Cache → Insight → 4 Techniques → Benchmarks → Papers
- Scroll-triggered animations, interactive visualizations
- Entropy heatmap, compression pipeline, token importance charts
- Glossary of all technical terms
- Dark theme, responsive, self-contained HTML (679 lines)

Updates pages workflow to deploy site/ alongside wasm/ demo.
URL: quantumaikr.github.io/quant.cpp/guide/

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

Author: unamedkr

.github/workflows/pages.yml

@@ -5,6 +5,7 @@ on:
     branches: [main]
     paths:
       - 'wasm/**'
+      - 'site/**'
       - '.github/workflows/pages.yml'
   workflow_dispatch:
 
@@ -32,12 +33,14 @@ jobs:
 
       - name: Prepare pages directory
         run: |
-          mkdir -p _site
+          mkdir -p _site _site/guide
+          # WASM demo (root)
           cp wasm/index.html _site/
-          cp wasm/quant.js _site/
-          cp wasm/quant.wasm _site/
-          # COOP/COEP headers for SharedArrayBuffer support
+          cp wasm/quant.js _site/ 2>/dev/null || true
+          cp wasm/quant.wasm _site/ 2>/dev/null || true
           cp wasm/_headers _site/_headers 2>/dev/null || true
+          # Educational guide (/guide)
+          cp site/index.html _site/guide/ 2>/dev/null || true
 
       - name: Setup Pages
         uses: actions/configure-pages@v5