Upgrade Vitest 2 to 4

[smartlabsAT]

Description

Vitest 4 is available (currently on ^2.1.9).

Packages to update

• vitest: ^2.1.9 -> 4.1.2
• @vitest/coverage-v8: 2.1.9 -> 4.1.2

Breaking Changes to investigate

• Config changes in vitest.config.ts
• Coverage config changes
• Test API changes

Tasks

• Read Vitest 4 migration guide
• Update vitest and @vitest/coverage-v8
• Update config if needed
• Verify all tests pass (pnpm test:ci)
• Verify coverage reports