fix(#28): disable BreakRule right arrow until selection made

- BreakRuleStep now starts with no selection when not prefilled
- Right arrow disabled and dimmed until a rule is chosen (like game type)
- Keeps auto-advance on clicking a rule

Refs #28

src/components/screens/NewGameScreen.tsx

@@ -147,7 +147,7 @@ export default function NewGameScreen({
         <BreakRuleStep
           onNext={handleBreakRuleNext}
           onCancel={handleStepBack}
-          initialValue={(data.breakRule as any) || (typeof window !== 'undefined' ? (localStorage.getItem('lastBreakRule') as any) : 'winnerbreak') || 'winnerbreak'}
+          initialValue={(data.breakRule as any) || (typeof window !== 'undefined' ? (localStorage.getItem('lastBreakRule') as any) : '') || ''}
         />
       )}