feat(ui): Mission-Control-Kacheln behalten Position und Identitaetsfarbe ueber Handoffs

Ein Handoff schloss die alte Pane und haengte die neue hinten an -- die Kachel
sprang ans Ende und das ganze Grid ordnete sich neu. Die neue Pane wird jetzt am
Index der alten eingesetzt.

Dazu bekommt jede Kachel eine aus IdentityKey (Default: TaskId) abgeleitete Farbe:
3px-Streifen links am Tile, Punkt im Focus-Mode-Tab. Kein State, keine Persistenz --
derselbe Task faerbt nach App-Neustart gleich, und ein Handoff erbt die Farbe, weil
er dieselbe TaskId behaelt. Nur kuehle Hues, damit nichts als Status gelesen wird.

src/ClaudeDo.Ui/Design/Tokens.axaml

@@ -104,6 +104,16 @@
   <SolidColorBrush x:Key="RoadblockTintBrush"       Color="#1FD4A574" />
   <SolidColorBrush x:Key="RoadblockTintBorderBrush" Color="#4CD4A574" />
 
+  <!-- Mission Control tile identity colours. Cool hues only, on purpose: the warm/green half of
+       the wheel is taken by the status semantics above, and an identity strip must never read as
+       "running"/"review"/"failed". -->
+  <SolidColorBrush x:Key="Identity1Brush" Color="#5FA8C8" />
+  <SolidColorBrush x:Key="Identity2Brush" Color="#4FA396" />
+  <SolidColorBrush x:Key="Identity3Brush" Color="#7E88CC" />
+  <SolidColorBrush x:Key="Identity4Brush" Color="#A57BB5" />
+  <SolidColorBrush x:Key="Identity5Brush" Color="#C77FA0" />
+  <SolidColorBrush x:Key="Identity6Brush" Color="#5C78B8" />
+
   <!-- Merge editor (3-pane conflict resolver) block tints -->
   <SolidColorBrush x:Key="MergeOursTintBrush"     Color="#1F7C9166" /> <!-- ours side (moss) -->
   <SolidColorBrush x:Key="MergeTheirsTintBrush"   Color="#1FD4A574" /> <!-- theirs side (amber) -->

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

@@ -19,6 +19,25 @@ public sealed partial class ConPtyPaneViewModel : ViewModelBase, IDisposable
     // Only a task-based pane can be submitted for review (an ad-hoc directory session has no task).
     public bool IsTaskBased => TaskId is not null;
 
+    /// <summary>Stable key behind <see cref="IdentityColorKey"/>. Defaults to the task id, so a
+    /// handoff — same task, new pane — keeps its colour for free; an ad-hoc pane gets a fresh one.
+    /// Settable so a handoff that mints a new key can inherit the outgoing pane's.</summary>
+    public string IdentityKey { get; init; }
+
+    /// <summary>Resource key of this tile's identity colour (via DotBrushConverter). Derived from
+    /// <see cref="IdentityKey"/>, never stored — the colour survives restarts without persistence.</summary>
+    public string IdentityColorKey => $"Identity{StableIndex(IdentityKey, 6) + 1}";
+
+    // 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)
+    {
+        uint hash = 2166136261;
+        foreach (var c in value)
+            hash = (hash ^ c) * 16777619;
+        return (int)(hash % (uint)buckets);
+    }
+
     /// <summary>Set by the host for a list-handler run ("Let Claude handle it" / "Let Claude merge
     /// the reviews") pane -- shows the "Abandon run" action. Plain mutable property, not
     /// <see cref="ObservableProperty"/>: the host sets it once right after construction, before the
@@ -70,6 +89,7 @@ public sealed partial class ConPtyPaneViewModel : ViewModelBase, IDisposable
         Func<System.Threading.Tasks.Task<TerminalLaunchDescriptor>> descriptorFactory)
     {
         TaskId = taskId;
+        IdentityKey = taskId ?? Guid.NewGuid().ToString("n");
         _displayTitle = displayTitle;
         _descriptorFactory = descriptorFactory;
         Subscribe(Terminal);

src/ClaudeDo.Ui/ViewModels/MissionControlViewModel.cs

@@ -408,6 +408,11 @@ public sealed partial class MissionControlViewModel : ViewModelBase, IDisposable
         if (string.IsNullOrEmpty(taskId) || survivingTaskIds is not { Count: > 0 }) return;
         OpenRequested?.Invoke();
 
+        // Keep the tile where it was: the incoming phase re-enters at the outgoing pane's slot
+        // instead of being appended, so a handoff doesn't reshuffle every other tile in the grid.
+        var slot = ConPtySessions.FirstOrDefault(s => s.TaskId == taskId) is { } first
+            ? ConPtySessions.IndexOf(first)
+            : (int?)null;
         foreach (var stale in ConPtySessions.Where(s => s.TaskId == taskId).ToList())
             CloseConPtySession(stale);
 
@@ -428,7 +433,7 @@ public sealed partial class MissionControlViewModel : ViewModelBase, IDisposable
 
         AddConPtyPane(new ConPtyPaneViewModel(taskId, title,
             () => DescribeAsync(() => _worker.GetMergeHelperHandoffLaunchSpecAsync(taskId, survivingTaskIds, nextPhase)))
-            { IsListHandler = true });
+            { IsListHandler = true }, slot);
     }
 
     // The 5h usage window is about to run out under this handler session: type the worker's warning
@@ -446,14 +451,14 @@ public sealed partial class MissionControlViewModel : ViewModelBase, IDisposable
 
     // Wires a freshly built pane and shows it immediately — the pane resolves its own launch spec,
     // so the tile is on screen (spinner running) while the worker is still preparing the worktree.
-    private void AddConPtyPane(ConPtyPaneViewModel pane)
+    private void AddConPtyPane(ConPtyPaneViewModel pane, int? index = null)
     {
         pane.ErrorReported += OnConPtyPaneError;
         pane.CloseRequested += OnPaneCloseRequested;
         pane.SubmitForReviewRequested += OnPaneSubmitForReview;
         pane.SessionDiedAfterStartup += OnPaneSessionDied;
         pane.AbandonRunRequested += OnPaneAbandonRun;
-        ConPtySessions.Add(pane);
+        ConPtySessions.Insert(Math.Min(index ?? ConPtySessions.Count, ConPtySessions.Count), pane);
         pane.Start();
     }
 

src/ClaudeDo.Ui/Views/MissionControl/ConPtyPaneView.axaml

@@ -4,11 +4,16 @@
              xmlns:views="using:ClaudeDo.Ui.Views"
              xmlns:loc="using:ClaudeDo.Ui.Localization"
              xmlns:conv="using:Avalonia.Data.Converters"
+             xmlns:cconv="using:ClaudeDo.Ui.Converters"
              x:DataType="vm:ConPtyPaneViewModel"
              x:Class="ClaudeDo.Ui.Views.MissionControl.ConPtyPaneView">
   <Border Classes="monitor-pane" BorderThickness="1" CornerRadius="10" ClipToBounds="True">
     <DockPanel LastChildFill="True">
 
+      <!-- Identity strip: same colour for the same session across handoffs and restarts. -->
+      <Border DockPanel.Dock="Left" Width="3"
+              Background="{Binding IdentityColorKey, Converter={x:Static cconv:DotBrushConverter.Instance}}" />
+
       <!-- Header: title + close -->
       <Border DockPanel.Dock="Top"
               Background="{DynamicResource Surface2Brush}"

src/ClaudeDo.Ui/Views/MissionControl/MissionControlView.axaml

@@ -84,7 +84,11 @@
                     IsVisible="{Binding IsFocusMode}">
           <TabControl.ItemTemplate>
             <DataTemplate x:DataType="vmm:ConPtyPaneViewModel">
-              <TextBlock Text="{Binding DisplayTitle}" TextTrimming="CharacterEllipsis" MaxWidth="160" />
+              <StackPanel Orientation="Horizontal" Spacing="6">
+                <Ellipse Width="7" Height="7" VerticalAlignment="Center"
+                         Fill="{Binding IdentityColorKey, Converter={x:Static conv:DotBrushConverter.Instance}}" />
+                <TextBlock Text="{Binding DisplayTitle}" TextTrimming="CharacterEllipsis" MaxWidth="160" />
+              </StackPanel>
             </DataTemplate>
           </TabControl.ItemTemplate>
         </TabControl>

tests/ClaudeDo.Ui.Tests/ViewModels/MissionControlViewModelTests.cs

@@ -747,6 +747,30 @@ public class MissionControlViewModelTests : IDisposable
         Assert.Equal(0, SubscriberCount(outgoingPane, "SubmitForReviewRequested"));
     }
 
+    // The handoff replaces a tile in place -- appending it would push it to the end of the grid and
+    // reshuffle every other tile on every phase change.
+    [Fact]
+    public async Task OpenMergeHelperHandoffConPtySessionAsync_KeepsPanePosition()
+    {
+        var worker = new FakeWorker();
+        using var vm = BuildVm(worker);
+        var dir = Path.Combine("C:", "Some", "Path");
+        await vm.OpenAdHocConPtySessionAsync(dir);
+        await vm.OpenMergeHelperConPtySessionAsync("L1", new[] { "t1" });
+        await vm.OpenAdHocConPtySessionAsync(dir);
+        var taskId = vm.ConPtySessions[1].TaskId!;
+        var color = vm.ConPtySessions[1].IdentityColorKey;
+
+        await vm.OpenMergeHelperHandoffConPtySessionAsync(taskId, new[] { "t1" }, "wait");
+
+        Assert.Equal(3, vm.ConPtySessions.Count);
+        Assert.Equal(taskId, vm.ConPtySessions[1].TaskId);
+        Assert.Equal(taskId, vm.Panes[1].TaskId);
+        // Same task, new pane -- the identity colour has to survive the handoff, or the tile the
+        // user was tracking changes colour mid-run.
+        Assert.Equal(color, vm.ConPtySessions[1].IdentityColorKey);
+    }
+
     [Fact]
     public async Task OpenMergeHelperHandoffConPtySessionAsync_SubmitForReview_ResolvesToSurvivingPane()
     {