The app now starts I18nProvider in zh-CN when no saved language exists, while preserving explicit saved choices. The login-required Ant Design modal also uses the v6 mask.closable shape so the console no longer warns about maskClosable.
Constraint: First-run locale should not override an existing saved language preference
Constraint: Ant Design 6 deprecates maskClosable on Modal.confirm
Rejected: Keep browser-language detection | first entry needs deterministic Simplified Chinese
Confidence: high
Scope-risk: narrow
Directive: Keep provider-less useI18n fallback stable for isolated tests unless all callers are wrapped in I18nProvider
Tested: npm run test:run -- src/i18n/__tests__/index.test.tsx src/components/__tests__/TemplateExplorerView.test.tsx src/components/__tests__/Header.test.tsx src/utils/__tests__/loginRequiredModal.test.ts src/utils/__tests__/authFetch.test.ts src/store/__tests__/userStore.test.ts
Tested: npm run build
Not-tested: npm run lint | existing Next 16 next lint script resolves to nonexistent /lint directory
jiajia
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