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.ts

@@ -22,10 +22,11 @@ export default defineConfig({
     // Retry configuration
     retry: parseInt(process.env.TEST_RETRY_ATTEMPTS || '2', 10),
     // Test reporter
-    reporters: process.env.CI ? ['default', 'json', 'junit'] : ['default'],
+    reporters: process.env.CI ? ['default', 'json', 'junit', 'html'] : ['default'],
     outputFile: {
       json: './test-results/results.json',
-      junit: './test-results/junit.xml'
+      junit: './test-results/junit.xml',
+      html: './test-results/html/index.html'
     },
     coverage: {
       provider: 'v8',