feat(ui): surface depends_on blocking in status chip, chain label, and detail pane

Usability-Audit 2026-09-10 found three gaps versus the dependency-chain-display
spec: a Queued task blocked on an unmet task_dependencies edge rendered the same
chip as one about to run, a cross-list predecessor silently dropped the
"after #N" chip, and the detail pane showed nothing about a wait at all.

- TaskRowViewModel gains IsBlockedByDependency/DependencyWaitLabel (extrinsic,
  assigned by TasksIslandViewModel like the existing chain fields); IsQueued/
  IsWaiting/StatusChipClass/StatusLabel/StatusChipTooltip now account for it
  alongside the existing BlockedByTaskId planning-chain link.
- TasksIslandViewModel.ApplyDependencyWaitState computes the blocked flag and
  wait label per row; a new RefreshExternalDependencyCacheAsync backfills
  Number/Title/Status for predecessors not loaded into the current list's
  Items (reusing the already-open DbContext, no new hub method), so
  BuildAfterLabel/blocking both resolve a listenfremder Vorgänger correctly.
- New "waiting" chip style (IslandStyles.axaml) and locale keys (en+de);
  TaskHeaderBar shows a "Waiting on #N" line bound straight to the same row.

Tests: TasksIslandChainTests (blocked/unblocked chip, cross-list predecessor),
DetailsIslandDependencyWaitTests (new), TaskRowViewModelNotificationsTests
updated for the new notification set.

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

@@ -112,11 +112,31 @@ public sealed partial class TaskRowViewModel : ViewModelBase
     [NotifyPropertyChangedFor(nameof(IsQueued))]
     [NotifyPropertyChangedFor(nameof(IsWaiting))]
     [NotifyPropertyChangedFor(nameof(StatusChipClass))]
+    [NotifyPropertyChangedFor(nameof(StatusLabel))]
+    [NotifyPropertyChangedFor(nameof(StatusChipTooltip))]
     [NotifyPropertyChangedFor(nameof(CanRemoveFromQueue))]
     private string? _blockedByTaskId;
     [ObservableProperty]
     [NotifyPropertyChangedFor(nameof(DependsOnTaskId))]
     private IReadOnlyList<string> _dependsOnTaskIds = [];
+    // Extrinsic — assigned by TasksIslandViewModel.ApplyDependencyWaitState, which alone has the
+    // cross-row graph (plus any cross-list predecessor lookup) needed to tell an unmet
+    // task_dependencies edge from a satisfied one. True only for the task_dependencies case;
+    // IsWaiting also ORs in the older BlockedByTaskId planning-chain link.
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(IsQueued))]
+    [NotifyPropertyChangedFor(nameof(IsWaiting))]
+    [NotifyPropertyChangedFor(nameof(StatusChipClass))]
+    [NotifyPropertyChangedFor(nameof(StatusLabel))]
+    [NotifyPropertyChangedFor(nameof(StatusChipTooltip))]
+    [NotifyPropertyChangedFor(nameof(CanRemoveFromQueue))]
+    private bool _isBlockedByDependency;
+    // The predecessor(s) this row is waiting on, rendered ("#42" or "#42, #57"), or null when not
+    // waiting. Prefers BlockedByTaskId's single predecessor (the planning chain "parent wins" the
+    // same way it does for the chain rail), else lists every unmet task_dependencies edge.
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(StatusChipTooltip))]
+    private string? _dependencyWaitLabel;
 
     // The single predecessor, or null when the task has none or several. The chain rail can only
     // draw a line, so a task waiting on n predecessors gets a ChainAfterLabel instead — see
@@ -275,8 +295,8 @@ public sealed partial class TaskRowViewModel : ViewModelBase
     // task). A live ConPTY session is that same shape but not parked — it reads "Interactive".
     public bool IsParked    => Status == TaskStatus.Idle && WorktreeState == ClaudeDo.Data.Models.WorktreeState.Active
                                && !HasInteractiveSession;
-    public bool IsQueued    => Status == TaskStatus.Queued && string.IsNullOrEmpty(BlockedByTaskId);
-    public bool IsWaiting   => Status == TaskStatus.Queued && !string.IsNullOrEmpty(BlockedByTaskId);
+    public bool IsQueued    => Status == TaskStatus.Queued && string.IsNullOrEmpty(BlockedByTaskId) && !IsBlockedByDependency;
+    public bool IsWaiting   => Status == TaskStatus.Queued && (!string.IsNullOrEmpty(BlockedByTaskId) || IsBlockedByDependency);
     public bool CanRemoveFromQueue => IsQueued || IsWaiting || HasQueuedSubtasks;
     // "Send to queue" is the single queue entry. On a finalized planning parent it queues the
     // plan (children) via CanQueuePlan; an Active (not-yet-finalized) planning parent is hidden —
@@ -412,9 +432,12 @@ public sealed partial class TaskRowViewModel : ViewModelBase
             : FailureReasonLabel;
 
     // Drives the status chip tooltip: an open interactive session takes priority (it's tappable),
-    // otherwise a Failed task's reason, otherwise no tooltip.
+    // then the predecessor(s) a waiting task is blocked on, then a Failed task's reason,
+    // otherwise no tooltip.
     public string? StatusChipTooltip
-        => HasInteractiveSession ? Loc.T("tasks.interactiveChipTip") : FailureReasonTooltip;
+        => HasInteractiveSession ? Loc.T("tasks.interactiveChipTip")
+         : IsWaiting && DependencyWaitLabel is not null ? Loc.T("tasks.waitingOnTip", DependencyWaitLabel)
+         : FailureReasonTooltip;
 
     public string DiffAdditionsText => $"+{DiffAdditions}";
     public string DiffDeletionsText => $"−{DiffDeletions}";
@@ -422,7 +445,8 @@ public sealed partial class TaskRowViewModel : ViewModelBase
 
     public string StatusLabel
         => HasInteractiveSession ? Loc.T("vm.taskStatus.interactive")
-         : IsParked ? Loc.T("vm.taskStatus.parked") : Status switch
+         : IsParked ? Loc.T("vm.taskStatus.parked")
+         : IsWaiting ? Loc.T("vm.taskStatus.waiting") : Status switch
     {
         TaskStatus.Idle             => Loc.T("vm.taskStatus.idle"),
         TaskStatus.Queued           => Loc.T("vm.taskStatus.queued"),
@@ -444,7 +468,7 @@ public sealed partial class TaskRowViewModel : ViewModelBase
 
     public string StatusChipClass => HasInteractiveSession
         ? "interactive"
-        : (Status, IsBlocked: !string.IsNullOrEmpty(BlockedByTaskId)) switch
+        : (Status, IsBlocked: !string.IsNullOrEmpty(BlockedByTaskId) || IsBlockedByDependency) switch
     {
         (TaskStatus.Running,            _) => "running",
         (TaskStatus.WaitingForReview,   _) => "review",