fix(ios): gate index>=4 appear-select on >5-tab overflow

[davidecallegaro]

Summary

Fixes #525.

On iOS, TabAppearModifier force-selects any tab with index >= 4 in onAppear to sync selection for tabs nested under iOS's "More" overflow tab. That overflow only exists when there are more than 5 visible tabs. With exactly 5 tabs there is no More tab, yet the 5th tab (index 4) still matches index >= 4, so it steals the selection whenever its scene re-appears — most visibly when the tab bar is re-shown after a screen hid it via .hideTabBar — causing a phantom tab switch that JS can't correct (selectedPage is a value-diffed controlled prop).

Change

Gate the force-select on actual overflow (filteredItems.count > 5), so it only runs when a real "More" tab exists.

 #if os(iOS)
-  if context.index >= 4, context.props.selectedPage != context.tabData.key {
+  if context.props.filteredItems.count > 5, context.index >= 4, context.props.selectedPage != context.tabData.key {
     context.onSelect(context.tabData.key)
   }
 #endif

Behavior

• >5 tabs (More menu): unchanged — the appear-sync still runs for overflowed tabs.
• ≤5 tabs: the spurious force-select no longer fires, so the 5th tab stops hijacking the selection on re-appear.

Testing

Verified on a 5-tab app (@bottom-tabs/react-navigation + expo-router) with a real device build: returning from a tabBarHidden screen no longer jumps to the 5th tab; normal tab switching and the >5-tab More flow are unaffected.