fix: mark as read when entry scrolls OFF screen, not on appear

Uses .onDisappear instead of .onAppear — entries are marked as read
only when they scroll past the top of the viewport, not when the
list first renders. Same behavior as proper RSS readers.

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

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

@@ -42,6 +42,12 @@ struct EntryListView: View {
                 }
                 .buttonStyle(.plain)
                 .contentShape(Rectangle())
+                .onDisappear {
+                    // Mark as read when card scrolls off the top
+                    if !entry.isRead {
+                        Task { await vm.markAsRead(entry) }
+                    }
+                }
                 .contextMenu {
                     entryContextMenu(entry: entry, vm: vm)
                 }
@@ -65,7 +71,7 @@ struct EntryListView: View {
                 }
                 .buttonStyle(.plain)
                 .contentShape(Rectangle())
-                .onAppear {
+                .onDisappear {
                     if !entry.isRead {
                         Task { await vm.markAsRead(entry) }
                     }