Minor UI improvements, state saving

Model/AppState.swift

@@ -1,20 +0,0 @@
-import AVFoundation
-import Foundation
-
-final class AppState: ObservableObject {
-    @Published var showingChannel = false
-    @Published var channelID: String = ""
-    @Published var channel: String = ""
-
-    func openChannel(from video: Video) {
-        channel = video.author
-        channelID = video.channelID
-        showingChannel = true
-    }
-
-    func closeChannel() {
-        showingChannel = false
-        channel = ""
-        channelID = ""
-    }
-}

Model/Channel.swift

@@ -0,0 +1,12 @@
+import AVFoundation
+import Defaults
+import Foundation
+
+struct Channel: Codable, Defaults.Serializable {
+    var id: String
+    var name: String
+
+    static func from(video: Video) -> Channel {
+        Channel(id: video.channelID, name: video.author)
+    }
+}