feat(sidebar): add a Home row above the collections list

Home was only reachable via the toolbar house icon — added a pinned
row at the top of the sidebar (matching a collection row's style,
highlighted when active) so it's a first-class nav target alongside
collections rather than toolbar-only.

Outpost/Features/Collections/CollectionsTreeView.swift

@@ -11,6 +11,8 @@ struct CollectionsTreeView: View {
     /// somewhere with no direct handle on the sidebar row it belongs
     /// under — see the identical parameter on `CollectionDocumentsOutline`.
     let externalRefreshToken: Int
+    let isShowingHome: Bool
+    let onSelectHome: () -> Void
     let onSelectDocument: (OutlineCollection, [OutlineDocument]) -> Void
     let onSearchInCollection: (OutlineCollection) -> Void
 
@@ -19,6 +21,8 @@ struct CollectionsTreeView: View {
         selectedCollection: Binding<OutlineCollection?>,
         selectedDocumentID: String?,
         externalRefreshToken: Int,
+        isShowingHome: Bool,
+        onSelectHome: @escaping () -> Void,
         onSelectDocument: @escaping (OutlineCollection, [OutlineDocument]) -> Void,
         onSearchInCollection: @escaping (OutlineCollection) -> Void
     ) {
@@ -26,6 +30,8 @@ struct CollectionsTreeView: View {
         _selectedCollection = selectedCollection
         self.selectedDocumentID = selectedDocumentID
         self.externalRefreshToken = externalRefreshToken
+        self.isShowingHome = isShowingHome
+        self.onSelectHome = onSelectHome
         self.onSelectDocument = onSelectDocument
         self.onSearchInCollection = onSearchInCollection
     }
@@ -37,6 +43,7 @@ struct CollectionsTreeView: View {
                     Task { await viewModel.load() }
                 }
             }
+            homeRow
             content
         }
         .task {
@@ -48,6 +55,32 @@ struct CollectionsTreeView: View {
         }
     }
 
+    /// Pinned above the collections list, not inside the scroll region —
+    /// Home isn't a collection, so it doesn't belong in `viewModel.collections`
+    /// or compete with them for scroll space.
+    private var homeRow: some View {
+        Button(action: onSelectHome) {
+            HStack(spacing: 6) {
+                Image(systemName: "house.fill")
+                    .font(.callout)
+                    .foregroundStyle(.secondary)
+                Text("Home")
+                    .font(.body)
+                Spacer(minLength: 0)
+            }
+            .padding(.vertical, 4)
+            .padding(.horizontal, 6)
+            .contentShape(Rectangle())
+            .background(
+                isShowingHome ? Color.accentColor.opacity(0.15) : Color.clear,
+                in: RoundedRectangle(cornerRadius: 6)
+            )
+        }
+        .buttonStyle(.plain)
+        .padding(.horizontal, 8)
+        .padding(.top, 4)
+    }
+
     @ViewBuilder
     private var content: some View {
         Group {

Outpost/Features/Collections/ContentView_macOS.swift

@@ -197,6 +197,8 @@ struct ContentView_macOS: View {
                 selectedCollection: $selectedCollection,
                 selectedDocumentID: documentPath.last?.id,
                 externalRefreshToken: documentsChangedToken,
+                isShowingHome: isShowingHome,
+                onSelectHome: goHome,
                 onSelectDocument: selectDocumentChain,
                 onSearchInCollection: searchInCollection
             )