rename app layout to shell and add window frame

examples/gallery/src/main.rs

@@ -34,8 +34,8 @@ use gpui_native_data::sidebar::{Sidebar, SidebarEntry};
 use gpui_native_data::tabs::{Tab, Tabs};
 use gpui_native_data::tree::{Tree, TreeItem};
 use gpui_native_icons::{IconAssets, IconRole, icon};
-use gpui_native_layout::app_layout::{AppLayout, LayoutState};
 use gpui_native_layout::resize_handle::ResizeHandle;
+use gpui_native_layout::shell::{LayoutState, Shell};
 use gpui_native_theme::{ActiveTheme as _, Size, Theme};
 use gpui_platform::application;
 
@@ -216,7 +216,7 @@ impl Gallery {
             .child("Center \u{2014} the dock lands here (L3)")
             .text_color(colors.muted_foreground);
 
-        AppLayout::new("gallery-shell", state)
+        Shell::new("gallery-shell", state)
             .left_sidebar(left_sidebar)
             .center(center)
             .right_sidebar(right_sidebar)