Add corner player layout on iPad and macOS

Preset-selected two-region layout: video in the top-left, a resizable
side column, and an optional region below the video. Pages are assigned
to regions per preset (Location picker in the page editor); the layout
falls back to the stacked widescreen layout below 900pt width, so Split
View and narrow windows degrade automatically.

- CornerPlayerLayout hosts the shared playerAreaForWidescreen builder,
  so the MPV hosting path is identical to the stacked layout
- Layout resolver in ExpandedPlayerSheet picks corner per layout pass;
  NavigationCoordinator.isCornerLayoutActive feeds the macOS window
  manager, which drops the aspect-ratio lock and auto-fit while corner
  is active (and restores them on exit, incl. fullscreen replay and
  window re-mounts)
- Side column width persisted via new cornerPanelColumnWidth setting
  (280-560pt, video column kept >= 480pt)
- Settings: layout mode picker (iPad/macOS) with automatic-fallback
  footer, per-page region picker when corner is on, region shown in
  the pages list

Yattee/Views/Settings/PlayerControls/PanelPageEditorView.swift

@@ -15,6 +15,7 @@ struct PanelPageEditorView: View {
 
     // Local state for immediate UI updates
     @State private var isEnabled: Bool = true
+    @State private var region: PanelRegion = .primary
     @State private var showDescription: Bool = true
     @State private var showStatsRow: Bool = true
     @State private var showChannelRow: Bool = true
@@ -32,6 +33,10 @@ struct PanelPageEditorView: View {
         Form {
             enabledSection
 
+            if PanelSettingsView.supportsCornerLayout, viewModel.panelLayoutMode == .corner {
+                regionSection
+            }
+
             if pageType == .info {
                 infoElementsSection
             }
@@ -73,6 +78,28 @@ struct PanelPageEditorView: View {
         }
     }
 
+    // MARK: - Region Section (corner layout)
+
+    private var regionSection: some View {
+        Section {
+            Picker(
+                String(localized: "panel.settings.page.region"),
+                selection: $region
+            ) {
+                ForEach(PanelRegion.allCases, id: \.self) { region in
+                    Text(region.displayName).tag(region)
+                }
+            }
+            .disabled(!viewModel.canEditActivePreset)
+            .onChange(of: region) { _, newValue in
+                guard newValue != configuration?.region else { return }
+                viewModel.setPanelPageRegion(newValue, for: pageType)
+            }
+        } footer: {
+            Text(String(localized: "panel.settings.page.region.footer"))
+        }
+    }
+
     // MARK: - Info Elements Section
 
     private var infoElementsSection: some View {
@@ -117,6 +144,7 @@ struct PanelPageEditorView: View {
 
     private func syncLocalState() {
         isEnabled = configuration?.isEnabled ?? true
+        region = configuration?.region ?? .primary
         let info = infoSettings
         showDescription = info.effectiveShowDescription
         showStatsRow = info.effectiveShowStatsRow

Yattee/Views/Settings/PlayerControls/PanelSettingsView.swift

@@ -14,9 +14,22 @@ struct PanelSettingsView: View {
 
     // Local state for immediate UI updates
     @State private var defaultVisibility: PanelDefaultVisibility = .hidden
+    @State private var layoutMode: PanelLayoutMode = .stacked
+
+    /// Corner layout exists on iPad and macOS only.
+    static var supportsCornerLayout: Bool {
+        #if os(macOS)
+        return true
+        #else
+        return UIDevice.current.userInterfaceIdiom == .pad
+        #endif
+    }
 
     var body: some View {
         List {
+            if Self.supportsCornerLayout {
+                layoutSection
+            }
             visibilitySection
             pagesSection
         }
@@ -40,6 +53,28 @@ struct PanelSettingsView: View {
         }
     }
 
+    // MARK: - Layout Section
+
+    private var layoutSection: some View {
+        Section {
+            Picker(
+                String(localized: "panel.settings.layoutMode"),
+                selection: $layoutMode
+            ) {
+                ForEach(PanelLayoutMode.allCases, id: \.self) { mode in
+                    Text(mode.displayName).tag(mode)
+                }
+            }
+            .disabled(!viewModel.canEditActivePreset)
+            .onChange(of: layoutMode) { _, newValue in
+                guard newValue != viewModel.panelLayoutMode else { return }
+                viewModel.syncPanelLayoutMode(newValue)
+            }
+        } footer: {
+            Text(String(localized: "panel.settings.layoutMode.footer"))
+        }
+    }
+
     // MARK: - Visibility Section
 
     private var visibilitySection: some View {
@@ -92,10 +127,15 @@ struct PanelSettingsView: View {
             HStack {
                 Label(page.pageType.displayName, systemImage: page.pageType.systemImage)
                 Spacer()
-                Text(page.isEnabled
-                    ? String(localized: "common.on")
-                    : String(localized: "common.off"))
-                    .foregroundStyle(.secondary)
+                if page.isEnabled, layoutMode == .corner, Self.supportsCornerLayout {
+                    Text(page.region.displayName)
+                        .foregroundStyle(.secondary)
+                } else {
+                    Text(page.isEnabled
+                        ? String(localized: "common.on")
+                        : String(localized: "common.off"))
+                        .foregroundStyle(.secondary)
+                }
             }
         }
     }
@@ -104,6 +144,7 @@ struct PanelSettingsView: View {
 
     private func syncLocalState() {
         defaultVisibility = viewModel.panelDefaultVisibility
+        layoutMode = viewModel.panelLayoutMode
     }
 }