Open Settings from yattee://settings

SettingsView owns its navigation stack, so pushing it onto a section's
stack rendered nothing. Select the Settings section where the layout has
one, otherwise present Home's settings sheet; open the Settings window on
macOS.

Yattee/Services/Navigation/NavigationCoordinator.swift

@@ -37,6 +37,12 @@ final class NavigationCoordinator {
     /// Sheets observe it via `.dismissesOnExternalNavigation(_:)`.
     var dismissPresentationsGeneration = 0
 
+    #if os(macOS)
+    /// Bumped to ask the main window to open the Settings window, which only a
+    /// view can do (`openWindow`).
+    var openSettingsWindowRequest = 0
+    #endif
+
     /// Whether the mini player is expanded to full screen.
     var isPlayerExpanded = false {
         didSet {
@@ -231,10 +237,27 @@ final class NavigationCoordinator {
 
     /// Navigate to a destination by pushing it onto the selected section's stack.
     func navigate(to destination: NavigationDestination) {
+        // Settings has its own navigation stack, so it can't be pushed onto a
+        // section's stack: it is a section, a sheet, or a window instead.
+        if case .settings = destination {
+            openSettings()
+            return
+        }
         router.push(destination)
         handoffManager?.updateActivity(for: destination)
     }
 
+    /// Shows Settings the way the current layout presents it: the Settings
+    /// section where the layout has one, otherwise the Home screen's sheet
+    /// (`NavigationRouter.ensureSelectionIsAvailable`), or on macOS its window.
+    func openSettings() {
+        #if os(macOS)
+        openSettingsWindowRequest += 1
+        #else
+        router.select(.settings)
+        #endif
+    }
+
     // MARK: - Sheet Presentation
 
     /// Dismiss the main window's sheets so external navigation lands on a

Yattee/Services/Navigation/NavigationRouter.swift

@@ -32,6 +32,11 @@ final class NavigationRouter {
     /// sidebar layout so it is created and loaded once.
     let sidebarManager = SidebarManager()
 
+    /// Set when Settings was requested in a layout without a Settings section
+    /// (the iPhone tab bar, unless the user added the tab). Home presents its
+    /// Settings sheet and clears it.
+    var pendingSettingsSheet = false
+
     @ObservationIgnored private var hasAppliedStartupTab = false
     @ObservationIgnored private var isSidebarManagerConfigured = false
 
@@ -139,6 +144,10 @@ final class NavigationRouter {
         case .sources:
             host = .home
             root = .mediaSources
+        case .settings:
+            host = .home
+            root = nil
+            pendingSettingsSheet = true
         default:
             host = .home
             root = current.navigationDestination()