Summary

• add focused Vitest coverage for arrays, dates, and money utilities
• expand string utility coverage for slugify, truncate, titleCase, and escapeHtml edge cases
• keep production code unchanged

Verification

• npm test
• npx tsc --noEmit
• npx vitest run --coverage --coverage.reporter=text-summary "--coverage.include=src/**/*.ts" "--coverage.exclude=src/**/*.test.ts"

Coverage after this change:

• Statements: 100% (80/80)
• Branches: 97.22% (35/36)
• Functions: 100% (15/15)
• Lines: 100% (80/80)