fix(ci): replace deprecated codecov test-results-action with codecov-action@v5

- Replace codecov/test-results-action@v1 with codecov/codecov-action@v5
- Add report_type: test_results parameter to distinguish from coverage upload
- Resolves deprecation warning in GitHub Actions workflow
- Both coverage and test results now use the same action with different configurations

This addresses the warning:
"This action is being deprecated in favor of 'codecov-action'.
Please update CI accordingly to use 'codecov-action@v5' with
'report_type: test_results'."

Author: doublegate

.github/workflows/core-ci.yml

@@ -67,10 +67,11 @@ jobs:
         verbose: true
 
     - name: Upload Test Results to Codecov
-      uses: codecov/test-results-action@v1
+      uses: codecov/codecov-action@v5
       if: always()
       with:
         token: ${{ secrets.CODECOV_TOKEN }}
+        report_type: test_results
         files: ./test-results/junit.xml
         flags: mcp-tests
         name: codecov-test-results