[iOS] Fix new menu item reordering

This introduces a similar `move(fromOffsets:toOffset:)` method to `BrowserMenuModel` that will be used when re-ordering visible items from SwiftUI hierarchies.

ios/brave-ios/Sources/BrowserMenu/BrowserMenuModel.swift

@@ -101,8 +101,26 @@ import SwiftUI
     reloadActions()
   }
 
+  /// Moves a visible action found at a given index to a given offset based on the way that
+  /// SwiftUI supplies source indexes + destination offsets.
+  ///
+  /// The destination offset not an index and instead a distance from the startIndex where an item
+  /// will be placed, which means the final offset is actually the endIndex (array count/"past the
+  /// end" index)
+  func moveVisibleActions(fromOffsets source: IndexSet, toOffset destination: Int) {
+    // For now we're just going to support moving a single item and drop any extras
+    guard let index = source.first, let action = visibleActions[safe: index] else { return }
+    reorderVisibleAction(
+      action,
+      to: destination >= visibleActions.endIndex ? visibleActions.endIndex - 1 : destination
+    )
+  }
+
+  /// Moves a visible action to a valid index
   func reorderVisibleAction(_ action: Action, to index: Int) {
-    if visibleActions.isEmpty || !visibleActions.contains(where: { action.id == $0.id }) {
+    if visibleActions.isEmpty || !visibleActions.contains(where: { action.id == $0.id })
+      || index >= visibleActions.endIndex
+    {
       return
     }
     var newRank: Double = 0

ios/brave-ios/Sources/BrowserMenu/CustomizeMenuView.swift

@@ -38,19 +38,8 @@ struct CustomizeMenuView: View {
               }
             }
           }
-          .onMove { indexSet, offset in
-            guard let index = indexSet.first, let action = model.visibleActions[safe: index] else {
-              return
-            }
-            // SwiftUI's move offset logic is a bit strange where the destination can be the
-            // count instead of the final valid index, so its safer to use SwiftUI's Collection
-            // API to handle it then get the valid destination index of that mutated array.
-            var ids = model.visibleActions.map(\.id)
-            ids.move(fromOffsets: indexSet, toOffset: offset)
-            guard let destination = ids.firstIndex(of: action.id) else {
-              return
-            }
-            model.reorderVisibleAction(action, to: destination)
+          .onMove { source, destination in
+            model.moveVisibleActions(fromOffsets: source, toOffset: destination)
           }
           .listRowBackground(Color(.secondaryBraveGroupedBackground))
         } header: {