Navigation architecture

Full detail behind the one-paragraph summary in the root AGENTS.md.

ContentView branches on platform.

Platform	Shell	Structure
macOS	ConsumerMacShell	NavigationSplitView over MacSidebar. Three destinations (Chat, Models, Advanced) plus the conversation list, which is scoped to Chat. Detail is ChatInterfaceView, SimplifiedModelsView, or ConsumerAdvancedHubView.
iOS	ConsumerCompactShell	ChatInterfaceView alone, plus sheets.

MacSidebarSelection has four cases: .chat (the transcript, whatever is current), .conversation(String), .models, and .advanced. Splitting .chat from .conversation is what lets ⌘1 land somewhere real before anything is saved. ⌘1/⌘2/⌘3 are published from the shell through focusedSceneValue(\.shellNavigationActions) because the chat cannot navigate away from itself. One @SceneStorage key, mac.sidebar.visibility, persists whether the sidebar is showing; column width is fixed by navigationSplitViewColumnWidth and the selection is re-derived from the current conversation on restore.

On iOS, Settings and the Advanced hub are sheets, both opened from the conversation drawer rather than the toolbar. Models is not the same kind of sheet: the chat presents ModelSelectionSheet (a picker, cross-platform), while the full SimplifiedModelsView management screen is reached through a NavigationLink inside CombinedSettingsView. On macOS SimplifiedModelsView is the .models sidebar destination.

ConsumerAdvancedHubView has five sections and eight rows:

Section	Rows	Availability
Connect	Host this Mac	macOS only (#if os(macOS))
Voice Utilities	Transcribe, Read Aloud, Voice Activity	both
Voice Utilities	Diarization	iOS only (#if canImport(UIKit))
Vision Utilities	Segmentation	iOS only, and so is the whole section
Agents	Talk, Computer Use	both
Management	Benchmarks	both

Storage and tool calling live in Settings and Manage Models instead.