Implement Comprehensive Test Cleanup Patterns from @mikkihugo's Analysis

Based on @mikkihugo's excellent test framework analysis in PR #44, we should implement better test cleanup patterns:\n\n## Issues Identified:\n- Pending promise errors in tests with background timers\n- Missing proper async cleanup in test teardown\n- Unhandled timers causing test runner warnings\n- Need for consistent test utilities\n\n## Proposed Solutions:\n\n### 1. Test Cleanup Utilities\njavascript\n// Standardized cleanup for all async operations\nclass TestCleanup {\n constructor() {\n this.timers = new Set();\n this.promises = new Set();\n }\n \n registerTimer(timer) { this.timers.add(timer); }\n registerPromise(promise) { this.promises.add(promise); }\n \n async cleanup() {\n // Clear all timers\n this.timers.forEach(timer => clearTimeout(timer));\n // Await all promises\n await Promise.allSettled([...this.promises]);\n }\n}\n\n\n### 2. Improved Test Structure\n- Before/after hooks that properly clean up resources\n- Timeout wrappers for all async operations\n- Consistent error handling patterns\n\n### 3. Performance Test Utils\nImplement the missing PerformanceTestUtils mentioned in the analysis\n\n## Benefits:\n- Eliminate flaky tests\n- Faster test execution\n- Better CI/CD reliability\n- Easier test debugging\n\n## Credit\nThis issue is based on the thorough test analysis by @mikkihugo in PR #44, particularly the test-status.md report.\n\n/cc @mikkihugo