replace react-nav header hack with scroll edge interaction module

- new expo-scroll-edge-interaction native module (iOS-only) that sets up
  UIScrollEdgeElementContainerInteraction on iOS 26+
- new ScrollEdgeInteractionProvider context and hooks
- Layout.Screen gains `transparentHeader` prop
- Layout.Header.Outer auto-detects transparent mode from context
- List auto-registers scroll view and applies content inset

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

modules/expo-scroll-edge-interaction/expo-module.config.json

@@ -0,0 +1,6 @@
+{
+  "platforms": ["ios"],
+  "ios": {
+    "modules": ["ExpoScrollEdgeInteractionModule"]
+  }
+}

modules/expo-scroll-edge-interaction/index.ts

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+export type {ScrollEdgeInteractionEdge} from './src/ExpoScrollEdgeInteraction.types'
+export {ExpoScrollEdgeInteractionView} from './src/ExpoScrollEdgeInteractionView'

modules/expo-scroll-edge-interaction/ios/ExpoScrollEdgeInteraction.podspec

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+Pod::Spec.new do |s|
+  s.name           = 'ExpoScrollEdgeInteraction'
+  s.version        = '1.0.0'
+  s.summary        = 'UIScrollEdgeElementContainerInteraction for React Native views'
+  s.description    = 'UIScrollEdgeElementContainerInteraction for React Native views'
+  s.author         = 'bluesky-social'
+  s.homepage       = 'https://github.com/bluesky-social/social-app'
+  s.platforms      = { :ios => '13.4', :tvos => '13.4' }
+  s.source         = { git: '' }
+  s.static_framework = true
+
+  s.dependency 'ExpoModulesCore'
+
+  # Swift/Objective-C compatibility
+  s.pod_target_xcconfig = {
+    'DEFINES_MODULE' => 'YES',
+    'SWIFT_COMPILATION_MODE' => 'wholemodule'
+  }
+
+  s.source_files = "**/*.{h,m,mm,swift,hpp,cpp}"
+end

modules/expo-scroll-edge-interaction/ios/ExpoScrollEdgeInteractionModule.swift

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+import ExpoModulesCore
+
+public class ExpoScrollEdgeInteractionModule: Module {
+  public func definition() -> ModuleDefinition {
+    Name("ExpoScrollEdgeInteraction")
+
+    View(ExpoScrollEdgeInteractionView.self) {
+      Prop("nodeHandle") { (view: ExpoScrollEdgeInteractionView, prop: Int?) in
+        view.nodeHandle = prop
+      }
+      Prop("scrollViewTag") { (view: ExpoScrollEdgeInteractionView, prop: Int?) in
+        view.scrollViewTag = prop
+      }
+      Prop("edge") { (view: ExpoScrollEdgeInteractionView, prop: String?) in
+        view.edge = prop
+      }
+    }
+  }
+}

modules/expo-scroll-edge-interaction/ios/ExpoScrollEdgeInteractionView.swift

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+import ExpoModulesCore
+import React
+
+class ExpoScrollEdgeInteractionView: ExpoView {
+  var nodeHandle: Int? {
+    didSet {
+      setupInteraction()
+    }
+  }
+
+  var scrollViewTag: Int? {
+    didSet {
+      setupInteraction()
+    }
+  }
+
+  var edge: String? {
+    didSet {
+      setupInteraction()
+    }
+  }
+
+  private var currentInteraction: NSObject?
+
+  private func setupInteraction() {
+    guard #available(iOS 26.0, *) else { return }
+
+    // Clean up old interaction
+    if let interaction = currentInteraction as? UIScrollEdgeElementContainerInteraction,
+       let headerView = findHeaderView() {
+      headerView.removeInteraction(interaction)
+      currentInteraction = nil
+    }
+
+    guard let nodeHandle = nodeHandle,
+          let scrollViewTag = scrollViewTag
+    else { return }
+
+    guard let headerView = appContext?.findView(withTag: nodeHandle, ofType: UIView.self) else {
+      return
+    }
+
+    // RCTScrollView wraps a UIScrollView — get the inner one
+    let scrollView: UIScrollView?
+    if let rctScrollView = appContext?.findView(withTag: scrollViewTag, ofType: RCTScrollView.self) {
+      scrollView = rctScrollView.scrollView
+    } else {
+      scrollView = appContext?.findView(withTag: scrollViewTag, ofType: UIScrollView.self)
+    }
+
+    guard let scrollView = scrollView else { return }
+
+    let interaction = UIScrollEdgeElementContainerInteraction()
+    interaction.edge = resolveEdge()
+    interaction.scrollView = scrollView
+    headerView.addInteraction(interaction)
+    currentInteraction = interaction
+  }
+
+  private func resolveEdge() -> NSDirectionalRectEdge {
+    switch edge {
+    case "bottom": return .bottom
+    case "left": return .leading
+    case "right": return .trailing
+    default: return .top
+    }
+  }
+
+  private func findHeaderView() -> UIView? {
+    guard let nodeHandle = nodeHandle else { return nil }
+    return appContext?.findView(withTag: nodeHandle, ofType: UIView.self)
+  }
+}

modules/expo-scroll-edge-interaction/src/ExpoScrollEdgeInteraction.types.ts

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+import {type ViewStyle} from 'react-native'
+
+export type ScrollEdgeInteractionEdge = 'top' | 'bottom' | 'left' | 'right'
+
+export interface ExpoScrollEdgeInteractionViewProps {
+  nodeHandle: number | null
+  scrollViewTag: number | null
+  edge?: ScrollEdgeInteractionEdge
+  children: React.ReactNode
+  style?: ViewStyle
+}

modules/expo-scroll-edge-interaction/src/ExpoScrollEdgeInteractionView.ios.tsx

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+import {requireNativeViewManager} from 'expo-modules-core'
+
+import {type ExpoScrollEdgeInteractionViewProps} from './ExpoScrollEdgeInteraction.types'
+
+const NativeView: React.ComponentType<ExpoScrollEdgeInteractionViewProps> =
+  requireNativeViewManager('ExpoScrollEdgeInteraction')
+
+export function ExpoScrollEdgeInteractionView({
+  children,
+  ...rest
+}: ExpoScrollEdgeInteractionViewProps) {
+  return <NativeView {...rest}>{children}</NativeView>
+}

modules/expo-scroll-edge-interaction/src/ExpoScrollEdgeInteractionView.tsx

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+import {type ExpoScrollEdgeInteractionViewProps} from './ExpoScrollEdgeInteraction.types'
+
+export function ExpoScrollEdgeInteractionView({
+  children,
+}: React.PropsWithChildren<ExpoScrollEdgeInteractionViewProps>) {
+  return children
+}