feat: Enhance unit test workflow with coverage reporting to Codecov

[pallavt]

Summary

• Emit coverage.xml from the unit test run (--cov-report=xml:coverage.xml, keeps term-missing).
• Upload it via codecov/codecov-action@v7 with CODECOV_TOKEN (fail_ci_if_error: true).

Notes

• Requires a CODECOV_TOKEN repo secret (Codecov dashboard → Settings).
• CI-only change in .github/workflows/unit-tests.yml; no Python code touched.

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge.

_{Reviews (6) · Last reviewed commit: "fix: Update git diff command and improve..."}

[tanmoysrt]

Can you instead use github ci and github bot to comment coverage info.

[pallavt]

@tanmoysrt switched from Codecov to GitHub-native PR comment.

• Removed codecov/codecov-action and the CODECOV_TOKEN requirement.

• Now emits coverage.xml and posts/updates a coverage comment via orgoro/coverage@v3.3.1 (SHA-pinned) using only secrets.GITHUB_TOKEN.

• Added permissions: contents: read, pull-requests: write; comment step runs on pull_request only.

No repo secrets or external service needed now.