Split Codecov reporting into separate unit-test and integration-test reports

[kurnakovv]

Summary

Adjust the Codecov reporting setup so coverage is published as two separate reports: one for unit tests and one for integration tests, instead of publishing only the integration-test report.

Problem

The current Codecov configuration/reporting appears to surface only integration test coverage. That makes it harder to distinguish unit-test coverage from integration-test coverage and reduces visibility into which test layer is contributing to overall coverage.

Proposed work

• Inspect the current CI and Codecov configuration.
• Update coverage collection/upload so unit test coverage and integration test coverage are generated independently.
• Ensure Codecov shows two distinct reports/flags rather than a single integration-only report.
• Verify the reporting works in pull requests and on the default branch.

Acceptance criteria

• Unit test coverage is uploaded to Codecov as its own report.
• Integration test coverage is uploaded to Codecov as its own report.
• Codecov no longer shows only the integration-test report.
• CI continues to pass after the reporting change.