The sidebar layout was gated on iPad idiom. It now appears wherever there
is room for it: regular width and regular height, or an iPad with
regular width (a short Stage Manager window keeps it). That covers the
Duo inner screen in both orientations, while large iPhones in landscape
and the Duo outer screen keep the tab bar. The subscriptions feed's
channel sidebar follows the same rule, and Sidebar settings are offered
on devices with a hinge.
SwiftUI's sidebarAdaptable TabView never shows a sidebar on iPhone
idiom, so the iOS sidebar layout now uses the NavigationSplitView with a
list sidebar that macOS already used, on iPad as well. The sidebar
layout shows the floating mini player instead of the tab bar accessory.
The tab bar and sidebar layouts each kept their own navigation paths and
selection, so swapping between them (resizing an iPad Stage Manager
window across the size-class breakpoint) lost every pushed screen and
re-applied the startup tab.
NavigationRouter now holds the selected section, a typed stack per
section keyed by SidebarItem.id, the search text and the sidebar
manager. Both layouts select with SidebarItem and render the router's
state; navigate(to:) pushes onto it directly instead of going through
an observed pendingNavigation, so a request made before a layout
appears is not lost, and a destination pushed before startup keeps its
section. When a layout can't show the selection (a sidebar channel in
the tab bar, a section hidden by customization) it lands on the section
that can host it with that screen pushed first.
This also fixes keyboard section commands in the tab bar layout and the
coordinator's stale tab on iPad. AppTab, pendingNavigation,
selectedSidebarItem and the unused SheetDestination/path API are gone,
and the iOS 18 and 26.1 root views are merged into AdaptiveTabView.
