fix: context-dependent FAB — play/pause on Reader, + on other tabs

Removed Tab(role: .search) — it was always visible on all tabs.
Now the floating action button changes based on selected tab:

- Home/Fitness: FAB (+) → opens food assistant (same as before)
- Reader: Play/Pause circle → toggles auto-scroll
  - Idle: play.fill icon, warm accent background
  - Playing: pause.fill icon, red background
  - Tapping toggles between play/pause

Speed controls appear as glass capsule above the FAB when playing.
Auto-scroll stops when switching away from Reader tab.

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

ios/Platform/Platform/ContentView.swift

@@ -50,35 +50,40 @@ struct MainTabView: View {
                     Tab("Reader", systemImage: "newspaper.fill", value: 2) {
                         ReaderTabView(vm: readerVM, isAutoScrolling: $isAutoScrolling, scrollSpeed: $scrollSpeed)
                     }
-
-                    // 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())
+            .tabBarMinimizeBehavior(.onScrollDown)
 
-            // Floating buttons (hidden on Reader tab)
-            if selectedTab != 2 {
-                VStack {
-                    Spacer()
-                    HStack(alignment: .bottom) {
+            // Floating action button — context-dependent
+            VStack {
+                Spacer()
+                HStack(alignment: .bottom) {
+                    if selectedTab != 2 {
                         FeedbackButton()
                             .padding(.leading, 20)
+                    }
 
-                        Spacer()
+                    Spacer()
 
+                    if selectedTab == 2 && showReader {
+                        // Reader: play/pause auto-scroll
+                        Button {
+                            withAnimation(.spring(duration: 0.3)) {
+                                isAutoScrolling.toggle()
+                            }
+                        } label: {
+                            Image(systemName: isAutoScrolling ? "pause.fill" : "play.fill")
+                                .font(.system(size: 18))
+                                .foregroundStyle(.white)
+                                .frame(width: 56, height: 56)
+                                .background(isAutoScrolling ? Color.red.opacity(0.85) : Color.accentWarm)
+                                .clipShape(Circle())
+                                .shadow(color: .black.opacity(0.2), radius: 8, y: 4)
+                        }
+                        .padding(.trailing, 20)
+                    } else {
+                        // Home/Fitness: FAB (+) for food
                         Button { showAssistant = true } label: {
                             Image(systemName: "plus")
                                 .font(.title2.weight(.semibold))
@@ -90,8 +95,8 @@ struct MainTabView: View {
                         }
                         .padding(.trailing, 20)
                     }
-                    .padding(.bottom, 70)
                 }
+                .padding(.bottom, 70)
             }
 
             // Auto-scroll speed controls (overlay when playing)
@@ -120,28 +125,12 @@ struct MainTabView: View {
                                 .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)
+                    .padding(.bottom, 140)
                     .transition(.move(edge: .bottom).combined(with: .opacity))
                 }
                 .animation(.spring(duration: 0.3), value: isAutoScrolling)
@@ -167,6 +156,10 @@ struct MainTabView: View {
             renderer.attachToWindow()
             await readerVM.loadInitial()
         }
+        .onChange(of: selectedTab) { _, newTab in
+            // Stop auto-scroll when leaving Reader
+            if newTab != 2 { isAutoScrolling = false }
+        }
     }
 
     private func foodAdded() {
@@ -233,11 +226,3 @@ struct AssistantSheetView: View {
         }
     }
 }
-
-// MARK: - Tab Bar Minimize (iOS 26+)
-
-struct TabBarMinimizeModifier: ViewModifier {
-    func body(content: Content) -> some View {
-        content.tabBarMinimizeBehavior(.onScrollDown)
-    }
-}