Add test coverage CI with PR comments and job summaries

[Copilot]

Adds automated test coverage reporting to CI pipeline. Coverage metrics are posted as PR comments and displayed in GitHub Actions job summaries.

Implementation

• Workflow (.github/workflows/test-coverage.yml)

  • Runs npm run test:coverage on PRs and pushes to main
  • Parses coverage-summary.json to extract metrics
  • Posts/updates PR comment with coverage table (avoids spam)
  • Writes to $GITHUB_STEP_SUMMARY for job output
  • Uploads HTML reports as artifacts (30-day retention)

• Permissions

  • contents: read, pull-requests: write, checks: write

• Documentation

  • Updated TESTING.md with CI coverage reporting section
  • Updated CONTRIBUTING.md to reference automated coverage reports

Example Output

## Test Coverage Report

| Metric | Coverage | Covered/Total |
|--------|----------|---------------|
| **Lines** | 45.89% | 218/475 |
| **Statements** | 45.99% | 224/487 |
| **Functions** | 51.78% | 29/56 |
| **Branches** | 33.58% | 44/131 |

<details>
<summary>Coverage Thresholds</summary>

Configured thresholds: Lines 38%, Statements 38%, Functions 35%, Branches 30%
</details>

Comment updates on subsequent pushes rather than creating new comments.

Original prompt

add the test coverage as a ci pipeline and the ci should report the coverage for each PR as a comment for npm run test:coverage. figure out the necessary permissions for the ci to output as a summary and make a comment to the PR.

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[github-actions]

Test Coverage Report

Metric	Coverage	Covered/Total
Lines	45.89%	218/475
Statements	45.79%	223/487
Functions	51.78%	29/56
Branches	32.82%	43/131

Coverage Thresholds

The project has the following coverage thresholds configured:

• Lines: 38%
• Statements: 38%
• Functions: 35%
• Branches: 30%

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Coverage report generated by `npm run test:coverage`

[Mossaka]

@copilot remove the visual indicators since we haven't established a baseline yet

[Copilot]

@copilot remove the visual indicators since we haven't established a baseline yet

Done. Removed all visual indicators (emojis) from the coverage report in commit fe9ba8d. The report now shows coverage metrics without status emojis.