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.

vitest.config.benchmark.ts

@@ -10,8 +10,9 @@ export default defineConfig({
       // Benchmark specific options
       include: ['tests/benchmarks/**/*.bench.ts'],
       reporters: process.env.CI 
-        ? [['./scripts/vitest-benchmark-json-reporter.js', {}]] 
+        ? ['default', ['./scripts/vitest-benchmark-json-reporter.js', {}]] 
         : ['default'],
+      outputFile: './benchmark-results.json',
     },
     setupFiles: [],
     pool: 'forks',