osx: wiring for opening a new window, but not connected to gesture yet

when I add `.tapGesture(count: 2)` to list items, this seems to block
single clicks because SwiftUI sucks. Need to find a better way to invoke
this.

osx/kordophone2/App.swift

@@ -18,6 +18,10 @@ struct KordophoneApp: App
             TextEditingCommands()
         }
 
+        WindowGroup(id: .transcriptWindow, for: Display.Conversation.self) { selectedConversation in
+            TranscriptWindowView(conversation: selectedConversation)
+        }
+
         Settings {
             PreferencesView()
         }
@@ -28,3 +32,42 @@ struct KordophoneApp: App
         print("Error: \(e.localizedDescription)")
     }
 }
+
+struct TranscriptWindowView: View
+{
+    @State private var transcriptViewModel = TranscriptView.ViewModel()
+    @State private var entryViewModel = MessageEntryView.ViewModel()
+    private let displayedConversation: Binding<Display.Conversation?>
+
+    public init(conversation: Binding<Display.Conversation?>) {
+        self.displayedConversation = conversation
+        transcriptViewModel.displayedConversation = conversation.wrappedValue
+        observeDisplayedConversationChanges()
+    }
+
+    private func observeDisplayedConversationChanges() {
+        withObservationTracking {
+            _ = displayedConversation.wrappedValue
+        } onChange: {
+            Task { @MainActor in
+                guard let displayedConversation = self.displayedConversation.wrappedValue else { return }
+                transcriptViewModel.displayedConversation = displayedConversation
+
+                observeDisplayedConversationChanges()
+            }
+        }
+    }
+
+    var body: some View {
+        VStack {
+            ConversationView(transcriptModel: $transcriptViewModel, entryModel: $entryViewModel)
+                .navigationTitle(displayedConversation.wrappedValue?.displayName ?? "Kordophone")
+                .selectedConversation(displayedConversation.wrappedValue)
+        }
+    }
+}
+
+extension String
+{
+    static let transcriptWindow = "TranscriptWindow"
+}

osx/kordophone2/ConversationListView.swift

@@ -11,6 +11,7 @@ struct ConversationListView: View
 {
     @Binding var model: ViewModel
     @Environment(\.xpcClient) private var xpcClient
+    @Environment(\.openWindow) private var openWindow
 
     var body: some View {
         List($model.conversations, selection: $model.selectedConversation) { conv in

osx/kordophone2/Models.swift

@@ -10,7 +10,7 @@ import XPC
 
 enum Display
 {
-    struct Conversation: Identifiable, Hashable
+    struct Conversation: Identifiable, Hashable, Codable
     {
         let id: String
         let name: String?