Channels layout improvements, other UI fixes

Shared/EnvironmentValues.swift

@@ -0,0 +1,13 @@
+import Foundation
+import SwiftUI
+
+private struct InNavigationViewKey: EnvironmentKey {
+    static let defaultValue = false
+}
+
+extension EnvironmentValues {
+    var inNavigationView: Bool {
+        get { self[InNavigationViewKey.self] }
+        set { self[InNavigationViewKey.self] = newValue }
+    }
+}