feat: complete Phase 3.8 - test infrastructure and CI/CD enhancements

- Add test result artifacts storage with multiple formats (JUnit, JSON, HTML)
- Configure GitHub Actions to upload and preserve test outputs
- Add PR comment integration with test summaries
- Create benchmark comparison workflow for PR performance tracking
- Add detailed test report generation scripts
- Configure artifact retention policies (30 days for tests, 90 for combined)
- Set up test metadata collection for better debugging

This completes all remaining test infrastructure tasks and provides
comprehensive visibility into test results across CI/CD pipeline.

.gitignore

@@ -40,6 +40,14 @@ logs/
 coverage/
 .nyc_output/
 test-results/
+test-reports/
+test-summary.md
+test-metadata.json
+benchmark-results.json
+benchmark-comparison.md
+benchmark-comparison.json
+benchmark-current.json
+benchmark-baseline.json
 tests/data/*.db
 tests/fixtures/*.tmp
 .vitest/