fix(settings): keep the sidebar visible instead of a full-window overlay

Settings now swaps into the same NavigationSplitView detail pane as
Home/collections (gated on AppNavigation.isShowingSettings) instead of
covering the whole root window — the sidebar, and the ability to just
click something else in it to leave Settings, stays available. Any
sidebar navigation (Home, a collection, a document) exits Settings.

Outpost/Features/Collections/ContentView_macOS.swift

@@ -4,6 +4,7 @@ import OutlineKit
 
 struct ContentView_macOS: View {
     @Environment(SessionStore.self) private var session
+    @Environment(AppNavigation.self) private var navigation
     /// The landing state — no collection selected yet is what Home actually
     /// means, so this starts `true` rather than auto-selecting the first
     /// collection the way this used to work.
@@ -75,7 +76,7 @@ struct ContentView_macOS: View {
             // `CollectionOverviewView`, so on Home it was a dead end: a
             // user could click it, type, and nothing would happen. The
             // sidebar's global search already covers "search everything."
-            if !(isShowingHome && documentPath.isEmpty) {
+            if !navigation.isShowingSettings && !(isShowingHome && documentPath.isEmpty) {
                 ToolbarItem(placement: .primaryAction) {
                     contextualSearchField
                 }
@@ -96,6 +97,7 @@ struct ContentView_macOS: View {
         isContextualSearchExpanded = false
         selectedCollection = nil
         isShowingHome = true
+        navigation.isShowingSettings = false
         replaceDocumentPath(with: [])
     }
 
@@ -144,7 +146,12 @@ struct ContentView_macOS: View {
     @ViewBuilder
     private var leadingToolbarContent: some View {
         Group {
-            if !trimmedGlobalQuery.isEmpty {
+            if navigation.isShowingSettings {
+                HStack(spacing: 6) {
+                    Image(systemName: "gearshape.fill")
+                    Text("Settings")
+                }
+            } else if !trimmedGlobalQuery.isEmpty {
                 HStack(spacing: 6) {
                     Image(systemName: "magnifyingglass")
                     Text("Search")
@@ -223,6 +230,7 @@ struct ContentView_macOS: View {
         globalSearchQuery = ""
         selectedCollection = collection
         isContextualSearchExpanded = true
+        navigation.isShowingSettings = false
         Task { @MainActor in
             isContextualSearchFocused = true
         }
@@ -233,11 +241,13 @@ struct ContentView_macOS: View {
     /// hierarchy immediately rather than just the leaf.
     private func selectDocumentChain(_ collection: OutlineCollection, _ chain: [OutlineDocument]) {
         selectedCollection = collection
+        navigation.isShowingSettings = false
         replaceDocumentPath(with: chain)
     }
 
     /// Flat-list / search-result clicks: no known ancestors, single-level push.
     private func openDocument(_ document: OutlineDocument) {
+        navigation.isShowingSettings = false
         replaceDocumentPath(with: [document])
     }
 
@@ -256,7 +266,13 @@ struct ContentView_macOS: View {
 
     @ViewBuilder
     private var detail: some View {
-        if let apiClient = session.apiClient {
+        if navigation.isShowingSettings {
+            // Deliberately not a `NavigationStack` destination or a separate
+            // window — it's its own page swapped into the same detail pane
+            // Home/collections use, so the sidebar (and the ability to just
+            // click something else in it) stays available while it's open.
+            SettingsView(onDone: { navigation.isShowingSettings = false })
+        } else if let apiClient = session.apiClient {
             // A fresh NavigationStack per collection (or when entering/leaving
             // search), so switching either also clears any pushed document.
             NavigationStack(path: $documentPath) {

Outpost/Root/RootView.swift

@@ -3,7 +3,6 @@ import OutlineKit
 
 struct RootView: View {
     @Environment(SessionStore.self) private var session
-    @Environment(AppNavigation.self) private var navigation
     @State private var welcomeName: String?
     @State private var starStore = StarStore()
     @AppStorage("outpost.fullLocalSyncEnabled") private var isFullLocalSyncEnabled = false
@@ -21,18 +20,9 @@ struct RootView: View {
                     .transition(.opacity)
                     .zIndex(1)
             }
-
-            #if os(macOS)
-            if navigation.isShowingSettings {
-                SettingsView(onDone: { navigation.isShowingSettings = false })
-                    .transition(.opacity)
-                    .zIndex(2)
-            }
-            #endif
         }
         .environment(starStore)
         .animation(.easeInOut(duration: 0.45), value: welcomeName != nil)
-        .animation(.easeInOut(duration: 0.2), value: navigation.isShowingSettings)
         .task {
             await session.refreshTeamInfoIfNeeded()
         }