ci: upload coverage to Codecov

[nficano]

Summary

• Add --cov-report=xml to the pytest invocation (the --cov=arcp source coverage is already configured in pyproject.toml).
• Upload coverage.xml to Codecov on the floor matrix entry only (one report is enough since the source coverage is identical across Python versions).
• fail_ci_if_error: false so a Codecov outage cannot break CI.

Pre-merge action required

• Add CODECOV_TOKEN as a repo secret (gh secret set CODECOV_TOKEN --repo agentruntimecontrolprotocol/python-sdk).
• Activate the repo at app.codecov.io.

Test plan

• Merge, confirm coverage uploads on next push to main.
• Check that the Codecov badge appears in the repo dashboard.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Chores
  • Enhanced test coverage reporting infrastructure to better track code quality metrics.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 9ab6a4db-ea59-4300-8496-c0c5a550b1cd

📥 Commits

Reviewing files that changed from the base of the PR and between 0584ed1 and 92cfa57.

📒 Files selected for processing (1)

• .github/workflows/test.yml

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Walkthrough

The test workflow now generates coverage reports in XML format during pytest execution and uploads the coverage data to Codecov exclusively for the Python 3.13 matrix entry, using a pinned action version and non-blocking error handling.

Changes

Coverage Reporting and Upload

Layer / File(s)	Summary
Coverage generation and Codecov upload .github/workflows/test.yml	Pytest now generates XML coverage reports via --cov-report=xml, and a new conditional step uploads the coverage to Codecov for the Python 3.13 matrix entry using codecov/codecov-action with non-blocking error handling.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'ci: upload coverage to Codecov' directly and concisely describes the main change: adding Codecov coverage uploads to the CI workflow.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/codecov-upload

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