feat(lists): assign a colour to a sidebar folder

Tints the folder name and its guide line; picked from a swatch row in the folder settings.

src/ClaudeDo.Ui/ViewModels/Islands/ListFolderNavItemViewModel.cs

@@ -16,6 +16,8 @@ public sealed partial class ListFolderNavItemViewModel : ViewModelBase
     public string? ParentFolderId { get; set; }
     [ObservableProperty] private string _name = "";
     [ObservableProperty] private string _iconKey = "Folder";
+    /// <summary>Hex colour for name + guide line; null = theme default.</summary>
+    [ObservableProperty] private string? _color;
     [ObservableProperty]
     [NotifyPropertyChangedFor(nameof(ShowCount))]
     private bool _isCollapsed;

src/ClaudeDo.Ui/ViewModels/Islands/ListsIslandViewModel.cs

@@ -352,6 +352,7 @@ public sealed partial class ListsIslandViewModel : ViewModelBase, IDisposable
                     Id = f.Id,
                     Name = f.Name,
                     IconKey = f.Icon ?? ListFolderIcon,
+                    Color = f.Color,
                     IsCollapsed = f.IsCollapsed,
                     ParentFolderId = f.ParentFolderId,
                 };
@@ -758,7 +759,7 @@ public sealed partial class ListsIslandViewModel : ViewModelBase, IDisposable
         if (folder is null || Dialogs is null || _services is null) return;
         var vm = _services.GetRequiredService<ListSettingsModalViewModel>();
         vm.ErrorReported += msg => ErrorReported?.Invoke(msg);
-        vm.BeginLoadFolder(folder.Id, folder.Name, folder.IconKey);
+        vm.BeginLoadFolder(folder.Id, folder.Name, folder.IconKey, folder.Color);
         await Dialogs.ShowListSettingsAsync(vm);
         // Rename, re-icon and delete all change the folder header (and delete releases its lists
         // back to the top level) — one reload covers every outcome.

src/ClaudeDo.Ui/ViewModels/Modals/ListSettingsModalViewModel.cs

@@ -115,6 +115,13 @@ public sealed partial class ListSettingsModalViewModel : ViewModelBase
 
     public const string DefaultIcon = "Dot";
 
+    /// <summary>Folder colour swatches; "" = no colour (theme default).</summary>
+    public static readonly string[] FolderColorOptions =
+        ["", "#D4A574", "#C87060", "#D9C27A", "#8B9D7A", "#6FB3A8", "#7FA7C9", "#A38BC9"];
+
+    /// <summary>Selected folder colour, "" for none.</summary>
+    [ObservableProperty] private string _folderColor = "";
+
     /// <summary>Default icon for folders, kept apart from <see cref="DefaultIcon"/> so lists never look like folders.</summary>
     public const string DefaultFolderIcon = "Folder";
 
@@ -229,8 +236,9 @@ public sealed partial class ListSettingsModalViewModel : ViewModelBase
     /// Opens the modal on an existing folder: name + icon only, no list config to load and
     /// nothing to fetch from the worker, so this needs no async counterpart.
     /// </summary>
-    public void BeginLoadFolder(string folderId, string name, string? icon)
+    public void BeginLoadFolder(string folderId, string name, string? icon, string? color = null)
     {
+        FolderColor = color ?? "";
         _folderId = folderId;
         IsFolder = true;
         CanToggleFolder = false;
@@ -375,6 +383,8 @@ public sealed partial class ListSettingsModalViewModel : ViewModelBase
         CloseAction?.Invoke();
     }
 
+    private static string? NullIfEmpty(string s) => s.Length == 0 ? null : s;
+
     private async Task SaveFolderAsync()
     {
         var name = string.IsNullOrWhiteSpace(Name) ? Loc.T("vm.listSettings.untitled") : Name;
@@ -388,6 +398,7 @@ public sealed partial class ListSettingsModalViewModel : ViewModelBase
                 Id = Guid.NewGuid().ToString("N"),
                 Name = name,
                 Icon = Icon,
+                Color = NullIfEmpty(FolderColor),
                 CreatedAt = DateTime.UtcNow,
             });
             // The create flow pre-creates a list row for this modal to save against; a folder
@@ -398,7 +409,7 @@ public sealed partial class ListSettingsModalViewModel : ViewModelBase
         }
         else
         {
-            await lists.RenameFolderAsync(_folderId, name, Icon);
+            await lists.RenameFolderAsync(_folderId, name, Icon, NullIfEmpty(FolderColor));
         }
 
         Saved = true;