Motivation

• Ensure the window-close-to-background behavior properly stops and resumes account synchronization and respects realtime mode and poll interval settings.

Description

• Add mocks for startSync and stopSync and a useAccountsQuery mock so tests can assert per-account sync calls.
• Mock the window onFocusChanged handler and extend the mocked uiState with pollInterval and realtimeMode, and refactor useUIStore mock to use a selector-based getState.
• Add assertions that stopSync is called for each account when the app is hidden instead of closed.
• Add tests that startSync is invoked with each account and the configured pollInterval when the hidden window regains focus, and that no resume occurs when realtimeMode is manual.

Testing

• Ran the updated unit tests for tests/app/useCloseToBackground.test.tsx with vitest, and they passed.
• Ran the test suite including the updated mocks and focused scenarios, and all related tests passed.

Codex Task