Improve CI configuration: eliminate duplicate runs, add concurrency

[mroderick]

What

Three changes to the CI workflow that reduce wasted compute and speed up iteration:

1. Scope workflow trigger to pull_request only

The previous on: [push, pull_request] triggered CI twice on every PR — once from the push event on the branch head, and once from the pull_request event. By scoping to PRs against master, each PR runs CI exactly once.

Also adds workflow_dispatch so CI can be triggered manually when needed (e.g., re-running after an infrastructure failure without a new push).

2. Add concurrency group with cancel-in-progress

When iterating on a PR, only the latest commit's CI result matters. The concurrency group (keyed on git ref) cancels any in-progress run before starting a new one. No more waiting for a stale run to finish before seeing the result you actually care about.

3. Removed push-to-master CI (part of commit 1)

Once branch protection requiring green builds is in place, every merge to master is guaranteed clean — making push-triggered CI on master redundant.

Benefits

• No more duplicate CI runs — PRs run CI once instead of twice, cutting total CI minutes by roughly half
• Fast iteration — pushing to a PR cancels the stale run immediately
• Green master guaranteed — branch protection ensures only passing code reaches master, making push-to-master CI unnecessary
• Faster deploys — no wait for redundant CI runs on master after merging

Setting up branch protection

After this merges, configure the repo to require green CI on master:

1. Go to Settings > Branches > Add rule (or edit the default)
2. Set Branch name pattern to master
3. Check Require status checks to pass before merging
4. Check Require branches to be up to date
5. Search and select the status checks — look for "Tests (Group *)" jobs (they appear after this workflow runs once)
6. Check Include administrators — admins can still bypass via the "Merge without waiting for requirements to be met" checkbox on the merge confirmation dialog
7. Ensure Allow force pushes and Allow deletions are unchecked
8. Save

Commits

Commit	Change
993ae65	scope workflow to pull_request only, eliminating duplicate runs
e74c52c	cancel in-progress CI on new commits

[mroderick]

I have updated the configuration of the branch protection

[olleolleolle]

Thank you!