ios: reorderable tab bar with more tabs, debug log export, AirPlay picker, more room above seeker

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

ios/Stemify/UI/Nav.swift

@@ -1,11 +1,32 @@
 import SwiftUI
 
 enum Tab: String, CaseIterable, Hashable {
-    case Library, Playlists, Search, Downloads, Settings
+    case Library, Songs, Albums, Artists, Genres, Playlists, Search, Downloads, Settings
+
+    static let defaultLayout: [Tab] = [.Library, .Playlists, .Search, .Downloads, .Settings]
+    /// iOS folds anything past five tabs into "More", so the bar holds at most this many.
+    static let maxVisible = 5
+
+    /// Parses the saved comma list; Settings is always kept so the app can't lock itself out.
+    static func layout(_ raw: String) -> [Tab] {
+        var out: [Tab] = []
+        for part in raw.split(separator: ",") {
+            if let t = Tab(rawValue: String(part)), !out.contains(t) { out.append(t) }
+        }
+        if out.isEmpty { return defaultLayout }
+        if !out.contains(.Settings) { out = Array(out.prefix(maxVisible - 1)) + [.Settings] }
+        return Array(out.prefix(maxVisible))
+    }
+
+    static func encode(_ tabs: [Tab]) -> String { tabs.map(\.rawValue).joined(separator: ",") }
 
     var icon: String {
         switch self {
         case .Library: "square.stack.fill"
+        case .Songs: "music.note"
+        case .Albums: "square.stack"
+        case .Artists: "music.mic"
+        case .Genres: "guitars.fill"
         case .Playlists: "music.note.list"
         case .Search: "magnifyingglass"
         case .Downloads: "arrow.down.circle.fill"
@@ -15,10 +36,10 @@ enum Tab: String, CaseIterable, Hashable {
 }
 
 enum Route: Hashable {
-    case Artists, Albums, Songs, Playlists
+    case Artists, Albums, Songs, Playlists, Genres, Downloads, TabBar
     case Eq, EqFilters(profileId: String), EqFilterPage(profileId: String, filterId: String)
     case PlexAccount, StemServer, Quality, Storage, Appearance
-    case ArtistPage(Artist), AlbumPage(Album), PlaylistPage(Playlist), StemPlaylistPage(String)
+    case GenrePage(String), ArtistPage(Artist), AlbumPage(Album), PlaylistPage(Playlist), StemPlaylistPage(String)
 }
 
 /// Tabs, their stacks and the Now Playing sheet: the things any screen can ask of the shell.
@@ -47,13 +68,30 @@ final class Ui {
         if t == tab { paths[t] = [] } else { tab = t }
     }
 
+    /// The tabs currently in the bar, in order.
+    var tabs: [Tab] { Tab.layout(AppGraph.shared.settings.tabLayout) }
+
+    /// Where library pages open: Library if it's in the bar, else the first tab that is.
+    private var home: Tab { tabs.contains(.Library) ? .Library : (tabs.first ?? .Settings) }
+
+    /// Downloads as its own tab, or pushed onto the current one when it's hidden.
+    func openDownloads() {
+        if tabs.contains(.Downloads) { selectTab(.Downloads) } else { push(.Downloads) }
+    }
+
+    /// Falls back to the first tab when the selected one was just removed from the bar.
+    func ensureValidTab() {
+        if !tabs.contains(tab) { tab = tabs.first ?? .Settings }
+    }
+
     func openNowPlaying() { nowPlayingOpen = true }
 
     /// Switches to the Library tab and pushes [r] there.
     func showInLibrary(_ r: Route) {
         nowPlayingOpen = false
-        tab = .Library
-        paths[.Library, default: []].append(r)
+        let t = home
+        tab = t
+        paths[t, default: []].append(r)
     }
 
     /// Switches to Settings and opens [r] (the Equalizer) there.