fix: inline title (no large title drop) + restore canvas background

1. .navigationBarTitleDisplayMode(.inline) — title stays at top
2. .background(Color.canvas) — restores warm cream background

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

ios/Platform/Platform/Features/Reader/Views/ReaderTabView.swift

@@ -19,8 +19,10 @@ struct ReaderTabView: View {
         NavigationStack {
             // Entry list as the main content — scrolls under the glass nav bar
             EntryListView(vm: vm, isCardView: isCardView, isAutoScrolling: $isAutoScrolling, scrollSpeed: scrollSpeed)
+                .background(Color.canvas)
                 .navigationTitle("Reader")
                 .navigationSubtitle(subtitleText)
+                .navigationBarTitleDisplayMode(.inline)
                 .toolbar {
                     if isAutoScrolling {
                         // Auto-scroll mode: speed controls in toolbar