ios: mac catalyst kb shortcuts

ios/Packages/Sybil/Sources/Sybil/SybilViewModel.swift

@@ -443,6 +443,34 @@ final class SybilViewModel {
         }
     }
 
+    func selectPreviousSidebarItem() {
+        selectAdjacentSidebarItem(offset: -1)
+    }
+
+    func selectNextSidebarItem() {
+        selectAdjacentSidebarItem(offset: 1)
+    }
+
+    private func selectAdjacentSidebarItem(offset: Int) {
+        let items = sidebarItems
+        guard !items.isEmpty else {
+            return
+        }
+
+        let currentIndex = selectedItem.flatMap { selection in
+            items.firstIndex { $0.selection == selection }
+        }
+        let startingIndex = currentIndex ?? (offset < 0 ? items.count : -1)
+        let nextIndex = (startingIndex + offset + items.count) % items.count
+        let nextSelection = items[nextIndex].selection
+
+        guard draftKind != nil || selectedItem != nextSelection else {
+            return
+        }
+
+        select(nextSelection)
+    }
+
     func deleteItem(_ selection: SidebarSelection) async {
         guard isAuthenticated else {
             return