CI: migrate away from deprecated codecov test-results-action

[shenanigansd]

No description provided.

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing br/codecov (8e0ea47) with main (d7ce9f5)}

Summary

✅ 2 untouched benchmarks

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.29%. Comparing base (d7ce9f5) to head (8e0ea47).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #136   +/-   ##
=======================================
  Coverage   88.29%   88.29%           
=======================================
  Files           3        3           
  Lines          94       94           
=======================================
  Hits           83       83           
  Misses         11       11           

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[Copilot]

Pull request overview

This PR migrates the GitHub Actions workflow from the deprecated codecov/test-results-action to the unified codecov/codecov-action@v5.5.2 for uploading test results. The migration maintains the same functionality while using the newer, supported action.

Changes:

• Added report_type: coverage parameter to the existing coverage upload step for clarity
• Replaced codecov/test-results-action@v1.2.1 with codecov/codecov-action@v5.5.2 for test results upload
• Added report_type: test_results parameter to distinguish test results from coverage reports

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