fix: deploy the concept-car write-up, not just the index

The Stage output step copied only index.html and assets/, so the
concept-car/ pages pushed in 904e0bb were never uploaded to Pages and
every URL under /concept-car/ returned 404 while the card linked to
them. Stage published write-up directories too, and assert they are
present before upload so a missing one fails the build instead of
shipping a dead link.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: RAEngineered

.github/workflows/deploy.yml

@@ -36,6 +36,18 @@ jobs:
           mkdir -p _site
           cp index.html _site/
           if [ -d assets ]; then cp -r assets _site/; fi
+          # Project write-ups hosted on this domain. Each is a directory of
+          # static pages; add new ones here or they will not be deployed.
+          for d in concept-car; do
+            if [ -d "$d" ]; then cp -r "$d" _site/; fi
+          done
+      - name: Verify staged output
+        run: |
+          test -f _site/index.html
+          test -f _site/concept-car/concept-car.html
+          test -f _site/concept-car/tabs.js
+          test -d _site/concept-car/assets
+          echo "staged: $(find _site -type f | wc -l) files"
       - uses: actions/upload-pages-artifact@v3
         with:
           path: _site