CI: run tests on pull requests

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

Author: louisabraham

.github/workflows/test.yml

@@ -1,5 +1,5 @@
 name: Test
-on: push
+on: [push, pull_request]
 jobs:
   test:
     timeout-minutes: 15