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.

docs/test-artifacts.md

@@ -0,0 +1,146 @@
+# Test Artifacts Documentation
+
+This document describes the comprehensive test result artifact storage system implemented in the n8n-mcp project.
+
+## Overview
+
+The test artifact system captures, stores, and presents test results in multiple formats to facilitate debugging, analysis, and historical tracking of test performance.
+
+## Artifact Types
+
+### 1. Test Results
+- **JUnit XML** (`test-results/junit.xml`): Standard format for CI integration
+- **JSON Results** (`test-results/results.json`): Detailed test data for analysis
+- **HTML Report** (`test-results/html/index.html`): Interactive test report
+- **Test Summary** (`test-summary.md`): Markdown summary for PR comments
+
+### 2. Coverage Reports
+- **LCOV** (`coverage/lcov.info`): Standard coverage format
+- **HTML Coverage** (`coverage/html/index.html`): Interactive coverage browser
+- **Coverage Summary** (`coverage/coverage-summary.json`): JSON coverage data
+
+### 3. Benchmark Results
+- **Benchmark JSON** (`benchmark-results.json`): Raw benchmark data
+- **Comparison Reports** (`benchmark-comparison.md`): PR benchmark comparisons
+
+### 4. Detailed Reports
+- **HTML Report** (`test-reports/report.html`): Comprehensive styled report
+- **Markdown Report** (`test-reports/report.md`): Full markdown report
+- **JSON Report** (`test-reports/report.json`): Complete test data
+
+## GitHub Actions Integration
+
+### Test Workflow (`test.yml`)
+
+The main test workflow:
+1. Runs tests with coverage using multiple reporters
+2. Generates test summaries and detailed reports
+3. Uploads artifacts with metadata
+4. Posts summaries to PRs
+5. Creates a combined artifact index
+
+### Benchmark PR Workflow (`benchmark-pr.yml`)
+
+For pull requests:
+1. Runs benchmarks on PR branch
+2. Runs benchmarks on base branch
+3. Compares results
+4. Posts comparison to PR
+5. Sets status checks for regressions
+
+## Artifact Retention
+
+- **Test Results**: 30 days
+- **Coverage Reports**: 30 days
+- **Benchmark Results**: 30 days
+- **Combined Results**: 90 days
+- **Test Metadata**: 30 days
+
+## PR Comment Integration
+
+The system automatically:
+- Posts test summaries to PR comments
+- Updates existing comments instead of creating duplicates
+- Includes links to full artifacts
+- Shows coverage and benchmark changes
+
+## Job Summary
+
+Each workflow run includes a job summary with:
+- Test results overview
+- Coverage summary
+- Benchmark results
+- Direct links to download artifacts
+
+## Local Development
+
+### Running Tests with Reports
+
+```bash
+# Run tests with all reporters
+CI=true npm run test:coverage
+
+# Generate detailed reports
+node scripts/generate-detailed-reports.js
+
+# Generate test summary
+node scripts/generate-test-summary.js
+
+# Compare benchmarks
+node scripts/compare-benchmarks.js benchmark-results.json benchmark-baseline.json
+```
+
+### Report Locations
+
+When running locally, reports are generated in:
+- `test-results/` - Vitest outputs
+- `test-reports/` - Detailed reports
+- `coverage/` - Coverage reports
+- Root directory - Summary files
+
+## Report Formats
+
+### HTML Report Features
+- Responsive design
+- Test suite breakdown
+- Failed test details with error messages
+- Coverage visualization with progress bars
+- Benchmark performance metrics
+- Sortable tables
+
+### Markdown Report Features
+- GitHub-compatible formatting
+- Summary statistics
+- Failed test listings
+- Coverage breakdown
+- Benchmark comparisons
+
+### JSON Report Features
+- Complete test data
+- Programmatic access
+- Historical comparison
+- CI/CD integration
+
+## Best Practices
+
+1. **Always Check Artifacts**: When tests fail in CI, download and review the HTML report
+2. **Monitor Coverage**: Use the coverage reports to identify untested code
+3. **Track Benchmarks**: Review benchmark comparisons on performance-critical PRs
+4. **Archive Important Runs**: Download artifacts from significant releases
+
+## Troubleshooting
+
+### Missing Artifacts
+- Check if tests ran to completion
+- Verify artifact upload steps executed
+- Check retention period hasn't expired
+
+### Report Generation Failures
+- Ensure all dependencies are installed
+- Check for valid test/coverage output files
+- Review workflow logs for errors
+
+### PR Comment Issues
+- Verify GitHub Actions permissions
+- Check bot authentication
+- Review comment posting logs