chore: run tests on actual commit not on merge commit

[astandrik]

Closes #2367

CI Results

Test Status: ⚠️ FLAKY

📊 Full Report

Total	Passed	Failed	Flaky	Skipped
318	316	0	2	0

😟 No changes in tests. 😕

Bundle Size: ✅

Current: 83.65 MB | Main: 83.65 MB
Diff: 0.00 KB (0.00%)

✅ Bundle size unchanged.

ℹ️ CI Information

• Test recordings for failed tests are available in the full report.
• Bundle size is measured for the entire 'dist' directory.
• 📊 indicates links to detailed reports.
• 🔺 indicates increase, 🔽 decrease, and ✅ no change in bundle size.

[Copilot]

Pull Request Overview

This PR updates the CI workflow to run tests on the actual commit from the pull request instead of the merge commit generated by GitHub.

• Updates the checkout step in the quality.yml workflow
• Uses the pull request head SHA to determine the reference for testing

Comments suppressed due to low confidence (1)

.github/workflows/quality.yml:27

• Consider adding an inline comment to clarify why this reference is used, which can help future maintainers understand the rationale for testing on the actual commit rather than the merge commit.

ref: ${{ github.event.pull_request.head.sha || github.sha }}