chore(#26): remove summary.png and add to .gitignore

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

Author: etoyama

.gitignore

@@ -52,6 +52,9 @@ htmlcov/
 .DS_Store
 Thumbs.db
 
+# Generated images
+summary.png
+
 # Logs
 *.log
 logs/