Skip CI for fork pull requests

Prevents workflow runs from outside contributors.
PRs from repo members and pushes to main still trigger CI.

Author: bearmug

.github/workflows/test.yml

@@ -11,6 +11,8 @@ concurrency:
 
 jobs:
   test:
+    # Only run for pushes or PRs from within the repo (not forks)
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository
     runs-on: ubuntu-latest
     strategy:
       matrix: