feat: auto-scroll play button in tab bar using Tab(role: .search)

Migrated to new Tab API (iOS 18+). The auto-scroll play button
uses Tab(role: .search) with systemImage: "play.fill" — this gives
the separated circular placement on the trailing side of the tab
bar, identical to the Photos app search icon.

Tapping the play icon:
- Switches to Reader tab
- Starts auto-scroll

When playing: a Liquid Glass speed control capsule appears above
the tab bar with [ - ] 1.00x [ + ] [ stop ].

Removed the old floating glass pill implementation.

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

ios/Platform/Platform/ContentView.swift

@@ -32,46 +32,53 @@ struct MainTabView: View {
     @State private var scrollSpeed: Double = 1.0
 
     private var showReader: Bool {
-        auth.currentUser?.id != 4 // Madiha doesn't see Reader
+        auth.currentUser?.id != 4
     }
 
     var body: some View {
         ZStack {
             TabView(selection: $selectedTab) {
+                Tab("Home", systemImage: "house.fill", value: 0) {
                     HomeView(selectedTab: $selectedTab)
-                    .tabItem { Label("Home", systemImage: "house.fill") }
-                    .tag(0)
+                }
 
+                Tab("Fitness", systemImage: "flame.fill", value: 1) {
                     FitnessTabView()
-                    .tabItem { Label("Fitness", systemImage: "flame.fill") }
-                    .tag(1)
+                }
 
                 if showReader {
+                    Tab("Reader", systemImage: "newspaper.fill", value: 2) {
                         ReaderTabView(vm: readerVM, isAutoScrolling: $isAutoScrolling, scrollSpeed: $scrollSpeed)
-                        .tabItem { Label("Reader", systemImage: "newspaper.fill") }
-                        .tag(2)
+                    }
+
+                    // Auto-scroll button — uses .search role for the separated
+                    // circular placement on the trailing side of the tab bar
+                    Tab("Auto", systemImage: "play.fill", value: 3, role: .search) {
+                        // When tapped, toggle auto-scroll instead of showing search
+                        Color.clear
+                            .onAppear {
+                                // Switch to Reader tab and start auto-scroll
+                                selectedTab = 2
+                                withAnimation(.spring(duration: 0.3)) {
+                                    isAutoScrolling = true
+                                }
+                            }
+                    }
                 }
             }
             .tint(Color.accentWarm)
             .modifier(TabBarMinimizeModifier())
 
-            // Floating buttons
+            // Floating buttons (hidden on Reader tab)
+            if selectedTab != 2 {
                 VStack {
                     Spacer()
                     HStack(alignment: .bottom) {
-                    if selectedTab != 2 {
                         FeedbackButton()
                             .padding(.leading, 20)
-                    }
 
                         Spacer()
 
-                    if selectedTab == 2 {
-                        // Reader: auto-scroll control at tab bar level
-                        readerAutoScrollPill
-                            .padding(.trailing, 8)
-                            .padding(.bottom, 0)
-                    } else {
                         Button { showAssistant = true } label: {
                             Image(systemName: "plus")
                                 .font(.title2.weight(.semibold))
@@ -83,10 +90,63 @@ struct MainTabView: View {
                         }
                         .padding(.trailing, 20)
                     }
-                }
                     .padding(.bottom, 70)
                 }
             }
+
+            // Auto-scroll speed controls (overlay when playing)
+            if isAutoScrolling && selectedTab == 2 {
+                VStack {
+                    Spacer()
+                    HStack(spacing: 12) {
+                        Button {
+                            scrollSpeed = max(0.25, scrollSpeed - 0.25)
+                        } label: {
+                            Image(systemName: "minus")
+                                .font(.caption.weight(.bold))
+                                .foregroundStyle(Color.accentWarm)
+                                .frame(width: 32, height: 32)
+                        }
+
+                        Text(String(format: "%.2fx", scrollSpeed))
+                            .font(.system(size: 13, weight: .bold, design: .monospaced))
+                            .foregroundStyle(Color.textPrimary)
+
+                        Button {
+                            scrollSpeed = min(3.0, scrollSpeed + 0.25)
+                        } label: {
+                            Image(systemName: "plus")
+                                .font(.caption.weight(.bold))
+                                .foregroundStyle(Color.accentWarm)
+                                .frame(width: 32, height: 32)
+                        }
+
+                        Divider()
+                            .frame(height: 20)
+
+                        Button {
+                            withAnimation(.spring(duration: 0.3)) {
+                                isAutoScrolling = false
+                            }
+                        } label: {
+                            Image(systemName: "stop.fill")
+                                .font(.system(size: 12))
+                                .foregroundStyle(.white)
+                                .frame(width: 34, height: 34)
+                                .background(Color.red.opacity(0.8))
+                                .clipShape(Circle())
+                        }
+                    }
+                    .padding(.horizontal, 14)
+                    .padding(.vertical, 8)
+                    .background(.ultraThinMaterial, in: Capsule())
+                    .shadow(color: .black.opacity(0.1), radius: 8, y: 2)
+                    .padding(.bottom, 70)
+                    .transition(.move(edge: .bottom).combined(with: .opacity))
+                }
+                .animation(.spring(duration: 0.3), value: isAutoScrolling)
+            }
+        }
         .confettiCannon(
             trigger: $confettiTrigger,
             num: 80,
@@ -104,8 +164,6 @@ struct MainTabView: View {
         .task {
             guard showReader else { return }
             let renderer = ArticleRenderer.shared
-            // Window is now available — attach WKWebView to force GPU
-            // compositor launch during startup, not first article tap
             renderer.attachToWindow()
             await readerVM.loadInitial()
         }
@@ -117,71 +175,6 @@ struct MainTabView: View {
         confettiTrigger += 1
         UINotificationFeedbackGenerator().notificationOccurred(.success)
     }
-
-    // MARK: - Reader Auto-Scroll Pill (tab bar level)
-
-    private var readerAutoScrollPill: some View {
-        Group {
-            if isAutoScrolling {
-                // Expanded: speed + stop
-                HStack(spacing: 8) {
-                    Button {
-                        scrollSpeed = max(0.25, scrollSpeed - 0.25)
-                    } label: {
-                        Image(systemName: "minus")
-                            .font(.caption2.weight(.bold))
-                            .foregroundStyle(Color.accentWarm)
-                            .frame(width: 28, height: 28)
-                    }
-
-                    Text(String(format: "%.2fx", scrollSpeed))
-                        .font(.system(size: 11, weight: .bold, design: .monospaced))
-                        .foregroundStyle(Color.textPrimary)
-
-                    Button {
-                        scrollSpeed = min(3.0, scrollSpeed + 0.25)
-                    } label: {
-                        Image(systemName: "plus")
-                            .font(.caption2.weight(.bold))
-                            .foregroundStyle(Color.accentWarm)
-                            .frame(width: 28, height: 28)
-                    }
-
-                    Button {
-                        withAnimation(.spring(duration: 0.3)) {
-                            isAutoScrolling = false
-                        }
-                    } label: {
-                        Image(systemName: "stop.fill")
-                            .font(.system(size: 11))
-                            .foregroundStyle(.white)
-                            .frame(width: 32, height: 32)
-                            .background(Color.red.opacity(0.8))
-                            .clipShape(Circle())
-                    }
-                }
-                .padding(.horizontal, 10)
-                .padding(.vertical, 6)
-                .background(.ultraThinMaterial, in: Capsule())
-                .transition(.scale(scale: 0.5).combined(with: .opacity))
-            } else {
-                // Collapsed: play button circle (like Photos search icon)
-                Button {
-                    withAnimation(.spring(duration: 0.3)) {
-                        isAutoScrolling = true
-                    }
-                } label: {
-                    Image(systemName: "play.fill")
-                        .font(.system(size: 15))
-                        .foregroundStyle(Color.accentWarm)
-                        .frame(width: 48, height: 48)
-                        .background(.ultraThinMaterial, in: Circle())
-                }
-                .transition(.scale(scale: 0.5).combined(with: .opacity))
-            }
-        }
-        .animation(.spring(duration: 0.3), value: isAutoScrolling)
-    }
 }
 
 // MARK: - Assistant Sheet