ci: add coverage report and summary to tests workflow (closes #3)

[xingyaoww]

Summary

• Add pytest-cov to dev dependencies
• Update CI to run pytest with coverage and produce Cobertura XML (coverage.xml)
• Add Code Coverage Summary action to generate a markdown/text summary and badge
• Post the coverage summary as a sticky PR comment on pull requests
• Upload coverage artifacts for inspection

Changes

• pyproject.toml: add pytest-cov in dev dependencies
• .github/workflows/tests.yml:
  • run pytest with --cov=openhands --cov-report=xml:coverage.xml --cov-report=term-missing
  • add irongut/CodeCoverageSummary@v1.3.0 step with badge output
  • add marocchino/sticky-pull-request-comment@v2 to comment results on PRs
  • upload coverage.xml and code-coverage-results.md as artifacts
  • trigger on both push and pull_request; set minimal permissions

Testing

• Local: executed pytest with coverage to verify coverage.xml generation (tests currently fail in local env but coverage report generation is validated). CI workflow will generate and publish the summary regardless of test outcomes due to if: always() on reporting steps.

Docs

• Not applicable.

Checklist

• CI updated to produce a coverage report
• Coverage summary included using Marketplace action
• PR references the issue and will close it when merged

Closes #3

@xingyaoww can click here to continue refining the PR

[github-actions]

Package	Line Rate	Health
.	100%	✔
core	86%	✔
core.runtime	86%	✔
core.runtime.tools	100%	✔
core.runtime.tools.execute_bash	100%	✔
core.runtime.tools.str_replace_editor	89%	✔
core.runtime.tools.str_replace_editor.utils	96%	✔
Summary	91% (667 / 736)	✔

[openhands-ai]

Looks like there are a few issues preventing this PR from being merged!

• GitHub Actions are failing:
  • Run tests

If you'd like me to help, just leave a comment, like

@OpenHands please fix the failing actions on PR #6 at branch `openhands/fix-issue-3-coverage`

Feel free to include any additional details that might help me get this PR into a better state.

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