Move /platform/detection vars into /env (#9707)

* Add platform vars to env

* Replace /platform/detection with /env

src/components/Layout/Header/index.tsx

@@ -6,7 +6,6 @@ import {useNavigation} from '@react-navigation/native'
 
 import {HITSLOP_30} from '#/lib/constants'
 import {type NavigationProp} from '#/lib/routes/types'
-import {isIOS} from '#/platform/detection'
 import {useSetDrawerOpen} from '#/state/shell'
 import {
   atoms as a,
@@ -29,6 +28,7 @@ import {
 } from '#/components/Layout/const'
 import {ScrollbarOffsetContext} from '#/components/Layout/context'
 import {Text} from '#/components/Typography'
+import {IS_IOS} from '#/env'
 
 export function Outer({
   children,
@@ -91,7 +91,7 @@ export function Content({
       style={[
         a.flex_1,
         a.justify_center,
-        isIOS && align === 'platform' && a.align_center,
+        IS_IOS && align === 'platform' && a.align_center,
         {minHeight: HEADER_SLOT_SIZE},
       ]}>
       <AlignmentContext.Provider value={align}>
@@ -186,7 +186,7 @@ export function TitleText({
         a.text_lg,
         a.font_semi_bold,
         a.leading_tight,
-        isIOS && align === 'platform' && a.text_center,
+        IS_IOS && align === 'platform' && a.text_center,
         gtMobile && a.text_xl,
         style,
       ]}
@@ -205,7 +205,7 @@ export function SubtitleText({children}: {children: React.ReactNode}) {
       style={[
         a.text_sm,
         a.leading_snug,
-        isIOS && align === 'platform' && a.text_center,
+        IS_IOS && align === 'platform' && a.text_center,
         t.atoms.text_contrast_medium,
       ]}
       numberOfLines={2}>