fix(ci): download slide decks from release during deployment

Slides were not loading on the live site because the PDFs exist in a
GitHub Release (tinytorch-slides-v0.1.0) but were never downloaded
during the build process. The .gitignore has *.pdf which prevents
slides from being committed to git.

Add a step to both deployment workflows to download all slide PDFs
from the release and inject them into _static/slides/ before deploy.

Fixes harvard-edge/cs249r_book#1162

.github/workflows/tinytorch-preview-dev.yml

@@ -95,6 +95,24 @@ jobs:
           echo "📦 Downloads folder contents:"
           ls -la tinytorch/site/_build/html/_static/downloads/ || echo "No downloads folder"
 
+      - name: 📊 Download slide decks from release
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          echo "📊 Downloading slide decks from GitHub release..."
+          mkdir -p tinytorch/site/_build/html/_static/slides
+
+          # Download all PDFs from the slides release
+          gh release download tinytorch-slides-v0.1.0 \
+            --repo harvard-edge/cs249r_book \
+            --pattern "*.pdf" \
+            --dir tinytorch/site/_build/html/_static/slides
+
+          echo ""
+          echo "📦 Slides folder contents:"
+          ls -la tinytorch/site/_build/html/_static/slides/ || echo "No slides folder"
+          echo "✅ Downloaded $(ls tinytorch/site/_build/html/_static/slides/*.pdf 2>/dev/null | wc -l) slide decks"
+
       - name: 🚀 Deploy to Dev Site via SSH
         env:
           SSH_DEPLOY_KEY: ${{ secrets.SSH_DEPLOY_KEY }}