fix(deploy): Include slides directory in GitHub Pages deployment

The deploy workflow was only copying the demos/ directory to the
GitHub Pages site, causing all slide URLs to return 404 errors.

Changes:
- Add slides/** to trigger paths so deployment runs on slide changes
- Copy slides/ directory to _site/ alongside demos/

This fixes: #29

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: jeremymanning

.github/workflows/deploy-demos.yml

@@ -7,6 +7,7 @@ on:
       - main
     paths:
       - 'demos/**'
+      - 'slides/**'
       - '.github/workflows/deploy-demos.yml'
 
   # Allow manual trigger from Actions tab
@@ -60,9 +61,11 @@ jobs:
 
       - name: Create build artifact
         run: |
-          echo "Preparing demos for deployment..."
+          echo "Preparing demos and slides for deployment..."
           mkdir -p _site/demos
+          mkdir -p _site/slides
           cp -r demos/* _site/demos/
+          cp -r slides/* _site/slides/
 
           # Create a .nojekyll file to bypass Jekyll processing
           touch _site/.nojekyll