Add tvOS Top Shelf extension

Surfaces Continue Watching, Recent Feed, and Recent Bookmarks in the
Apple TV Home top shelf when Yattee is focused. Tapping a tile opens
the video via the existing yattee://video/{id} deep link.

- New YatteeTopShelf app extension target (tvOS only). LD_ENTRY_POINT is
  overridden to _NSExtensionMain; the tv-app-extension product type
  defaults to _TVExtensionMain which is for the pre-tvOS-13 legacy API
  and crashes modern TVTopShelfContentProvider subclasses at launch.
- Main app writes per-section JSON snapshots (capped at 10 items each)
  to a shared App Group UserDefaults suite after bookmark, watch-history,
  and feed-cache changes, plus an initial write on launch.
- Enabled-sections list is mirrored to the same App Group so the
  extension can respect the user's selection without touching SwiftData.
- Settings → Top Shelf (tvOS only) lets the user toggle sections.
- Deep link playback shows a loading toast while video details are
  fetched, and an error toast if no source is configured.

Yattee/Core/AppGroup.swift

@@ -0,0 +1,12 @@
+import Foundation
+
+enum AppGroup {
+    static let identifier = "group.stream.yattee.app.shared"
+
+    /// UserDefaults key holding an ordered [String] of enabled TopShelfSection raw values.
+    static let enabledSectionsKey = "topShelf.enabledSections"
+
+    static var defaults: UserDefaults {
+        UserDefaults(suiteName: identifier) ?? .standard
+    }
+}

Yattee/Core/Settings/SettingsKey.swift

@@ -65,6 +65,9 @@ enum SettingsKey: String, CaseIterable {
     case homeSectionItemsLimit
     case homeSectionLayout
 
+    // Top Shelf (tvOS)
+    case topShelfSections
+
     // Tab Bar (compact size class)
     case tabBarItemOrder
     case tabBarItemVisibility
@@ -126,6 +129,8 @@ enum SettingsKey: String, CaseIterable {
              // Home layout — different UI paradigms per platform
              .homeShortcutOrder, .homeShortcutVisibility, .homeShortcutLayout,
              .homeSectionOrder, .homeSectionVisibility, .homeSectionItemsLimit, .homeSectionLayout,
+             // Top Shelf — tvOS only
+             .topShelfSections,
              // Tab bar (compact size class) layout
              .tabBarItemOrder, .tabBarItemVisibility, .tabBarStartupTab,
              // Sidebar layout/selection

Yattee/Core/Settings/SettingsManager+TopShelf.swift

@@ -0,0 +1,43 @@
+//
+//  SettingsManager+TopShelf.swift
+//  Yattee
+//
+//  tvOS Top Shelf settings.
+//
+
+import Foundation
+
+extension SettingsManager {
+    /// Ordered list of sections visible in the tvOS Top Shelf.
+    /// Inclusion means the section is shown; absence hides it.
+    var topShelfSections: [TopShelfSection] {
+        get {
+            if let cached = _topShelfSections { return cached }
+            guard let data = data(for: .topShelfSections),
+                  let saved = try? JSONDecoder().decode([TopShelfSection].self, from: data) else {
+                return TopShelfSection.defaultOrder
+            }
+            return saved
+        }
+        set {
+            _topShelfSections = newValue
+            if let data = try? JSONEncoder().encode(newValue) {
+                set(data, for: .topShelfSections)
+            }
+            let tsKey = modifiedAtKey(for: .topShelfSections)
+            let now = Date().timeIntervalSince1970
+            localDefaults.set(now, forKey: tsKey)
+            if iCloudSyncEnabled && syncSettings && !isInitialSyncPending {
+                ubiquitousStore.set(now, forKey: tsKey)
+            }
+            mirrorEnabledSectionsToAppGroup(newValue)
+        }
+    }
+
+    /// Mirrors the enabled-sections list to the App Group UserDefaults suite
+    /// so the tvOS Top Shelf extension can read the user's selection.
+    func mirrorEnabledSectionsToAppGroup(_ sections: [TopShelfSection]) {
+        let rawValues = sections.map(\.rawValue)
+        AppGroup.defaults.set(rawValues, forKey: AppGroup.enabledSectionsKey)
+    }
+}

Yattee/Core/Settings/TopShelfSection.swift

@@ -0,0 +1,30 @@
+import Foundation
+
+/// Sections that can appear in the tvOS Top Shelf.
+/// Stored ordered in `SettingsKey.topShelfSections` — inclusion = visible.
+enum TopShelfSection: String, Codable, CaseIterable, Identifiable, Sendable {
+    case continueWatching
+    case recentFeed
+    case recentBookmarks
+
+    var id: String { rawValue }
+
+    var localizedTitle: String {
+        switch self {
+        case .continueWatching: return String(localized: "home.section.continueWatching")
+        case .recentFeed: return String(localized: "home.section.feed")
+        case .recentBookmarks: return String(localized: "home.section.bookmarks")
+        }
+    }
+
+    /// UserDefaults key (under the app-group suite) holding the JSON snapshot for this section.
+    var snapshotKey: String {
+        switch self {
+        case .continueWatching: return "topShelf.continueWatching"
+        case .recentFeed: return "topShelf.recentFeed"
+        case .recentBookmarks: return "topShelf.recentBookmarks"
+        }
+    }
+
+    static let defaultOrder: [TopShelfSection] = [.continueWatching, .recentFeed, .recentBookmarks]
+}

Yattee/Core/SettingsManager.swift

@@ -109,6 +109,9 @@ final class SettingsManager {
     var _homeSectionItemsLimit: Int?
     var _homeSectionLayout: HomeSectionLayout?
 
+    // Top Shelf (tvOS)
+    var _topShelfSections: [TopShelfSection]?
+
     // Tab bar settings (compact size class only - iOS)
     var _tabBarItemOrder: [TabBarItem]?
     var _tabBarItemVisibility: [TabBarItem: Bool]?
@@ -453,6 +456,7 @@ final class SettingsManager {
         _homeSectionVisibility = nil
         _homeSectionItemsLimit = nil
         _homeSectionLayout = nil
+        _topShelfSections = nil
         _tabBarItemOrder = nil
         _tabBarItemVisibility = nil
         _sidebarMainItemOrder = nil