Localize setup detected language hint

[w287346141]

Summary:

• Localized the setup language picker detected-locale hint.
• Added test coverage for the zh-CN detected hint.

Verification:

• npm.cmd run test -- wizard.test.tsx
• npm.cmd run typecheck
• npm run verify

[w287346141]

Superseded by #21, which batches the setup wizard localization work and resolves the shared Wizard.tsx / tests/wizard.test.tsx conflicts ahead of review.