Function useNavigationGuard

Prevents accidental navigation away from the current page while active is true.

• Refresh / tab close: Shows the browser's native "Leave site?" dialog.
• Back / forward button: Pushes a history sentinel and intercepts popstate, setting dialogOpen to true so the consumer can show a confirmation UI.

When the user confirms via confirm(), onConfirmLeave is called if provided, otherwise history.back() fires to complete the original navigation.