Fix CI: handle missing assets/ in commit step

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: spicyfalafel

.github/workflows/docs.yml

@@ -37,6 +37,6 @@ jobs:
         run: |
           git config user.name "github-actions[bot]"
           git config user.email "github-actions[bot]@users.noreply.github.com"
-          git add assets/ docs/
+          git add assets/ docs/ 2>/dev/null || true
           git diff --cached --quiet || git commit -m "chore: optimize images + generate OG previews"
           git push