test: migrate from Jest to Vitest (Phase 1 complete)

- Remove Jest and all related packages
- Install Vitest with coverage support
- Create vitest.config.ts with path aliases
- Set up global test configuration
- Migrate all 6 test files to Vitest syntax
- Update TypeScript configuration for better Vitest support
- Create separate tsconfig.build.json for clean builds
- Fix all import/module issues in tests
- All 68 tests passing successfully
- Current coverage baseline: 2.45%

Phase 1 of testing suite improvement complete.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

docs/testing-strategy-ai-optimized.md

@@ -81,7 +81,7 @@ git push
 # Check Actions tab on GitHub - should see workflow running
 ```
 
-## Phase 1: Vitest Migration (Week 1)
+## Phase 1: Vitest Migration (Week 1) ✅ COMPLETED
 
 ### Task 1.1: Install Vitest