feat(ui): coloured dots for icon-less lists, guide line under chevron

Lists without an icon show a dot in a stable identity colour (same
palette/hash as Mission Control tiles); "Dot" is the new picker default.

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

@@ -1,4 +1,5 @@
 using ClaudeDo.Data.Models;
+using ClaudeDo.Ui.ViewModels.MissionControl;
 using CommunityToolkit.Mvvm.ComponentModel;
 
 namespace ClaudeDo.Ui.ViewModels.Islands;
@@ -30,7 +31,15 @@ public sealed partial class ListNavItemViewModel : ViewModelBase
     // DropHintAbove/Below, which mark an insertion point for list reordering.
     [ObservableProperty] private bool _isTaskDropTarget;
     // Settable (not init) so a list-settings icon change refreshes the row in place.
-    [ObservableProperty] private string? _iconKey;
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(IsDot))]
+    private string? _iconKey;
+
+    /// <summary>No icon picked — the row shows a coloured dot instead of a glyph.</summary>
+    public bool IsDot => IconKey is null or ListsIslandViewModel.ListIcon;
+
+    /// <summary>Identity colour of the dot, stable per list id across restarts.</summary>
+    public string DotColorKey => $"Identity{ConPtyPaneViewModel.StableIndex(Id, 6) + 1}";
     // The sidebar folder this row sits in (ListEntity.FolderId); null = top level.
     [ObservableProperty] private string? _folderId;
 }

src/ClaudeDo.Ui/ViewModels/MissionControl/ConPtyPaneViewModel.cs

@@ -30,7 +30,8 @@ public sealed partial class ConPtyPaneViewModel : ViewModelBase, IDisposable
 
     // FNV-1a, not string.GetHashCode: the latter is randomized per process, so the same task would
     // change colour on every app start.
-    private static int StableIndex(string value, int buckets)
+    /// <summary>Process-stable bucket for <paramref name="value"/>; also colours the sidebar list dots.</summary>
+    internal static int StableIndex(string value, int buckets)
     {
         uint hash = 2166136261;
         foreach (var c in value)

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

@@ -111,7 +111,7 @@ public sealed partial class ListSettingsModalViewModel : ViewModelBase
 
     public ObservableCollection<string> CommitTypeOptions { get; } = new(CommitTypeRegistry.Types);
 
-    public const string DefaultIcon = "Text";
+    public const string DefaultIcon = "Dot";
 
     /// <summary>Default icon for folders, kept apart from <see cref="DefaultIcon"/> so lists never look like folders.</summary>
     public const string DefaultFolderIcon = "Folder";
@@ -123,7 +123,7 @@ public sealed partial class ListSettingsModalViewModel : ViewModelBase
     public static readonly string[] IconOptions =
     [
         // general
-        "Folder", "Star", "Sun", "Calendar", "Clock", "Inbox", "Mail", "Text", "Search", "Grid",
+        "Dot", "Folder", "Star", "Sun", "Calendar", "Clock", "Inbox", "Mail", "Text", "Search", "Grid",
         // dev
         "Code", "Terminal", "Database", "Server", "Chip", "Bolt", "Wand", "Flask", "Shield",
         // status / flow