chore: gitignore /outputs dir from toolhub CLI test runs

The toolhub CLI (`toolhub.py call`) writes generated images to
outputs/<trace_id>/, which is test/session scratch. Never commit.

.gitignore

@@ -63,6 +63,7 @@ output
 .trace_test/
 .trace_test2/
 examples/**/output*/
+outputs/
 
 frontend/htmlTemplate/mock_data
 frontend/react-template/yarn.lock