feat(board): master-task board, non-destructive stall watchdog, review flow

Board is now a clean master-task view:
- GetBoardAsync returns only top-level (master) tasks; child-tasks render
  nested inside their parent card instead of as separate column cards, so a
  big task split into many sub-tasks stays one card (orphans treated as master)
- New DoneChildTaskCount on the DTO for real progress bars
- Child/detail consumers (GetChildren endpoint, TaskBridgeService) query
  children directly instead of scraping the flat board

Stall watchdog (replaces destructive auto-reset):
- StaleTaskRecoveryService.FlagStalledInProgressTasksAsync marks In-progress
  tasks with no activity past the threshold as stalled (activity event +
  Iris notification) WITHOUT resetting the column — no work is discarded.
  Idempotent: a task is not re-flagged until real progress happens
- BackgroundService now runs this watchdog (TaskRecovery:StalledMinutes=40,
  interval 10m); hard reset kept only on the explicit manual endpoint

Review flow (Bao/Iris only):
- POST tasks/{id}/approve (Review -> Done)
- POST tasks/{id}/request-changes (Review -> target, mandatory comment,
  ExpectedFrom=iris, notifies Iris)

Frontend:
- BoardCard component: master card with ball chip (who has it), progress from
  children, expand to show children grouped by agent with per-child state +
  stalled marker, stalled chip on the master, review action buttons
- Request-changes modal; tasks store approveReview/requestChanges actions

Tests: watchdog flag/idempotency + review threshold; 135 backend tests green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/Services/StaleTaskRecoveryService.cs

@@ -7,8 +7,81 @@ namespace Nexus.Api.Services;
 public sealed class StaleTaskRecoveryService(
     ITaskRepository taskRepository,
     IActivityRepository activityRepository,
-    ILiveUpdateService liveUpdateService) : IStaleTaskRecoveryService
+    ILiveUpdateService liveUpdateService,
+    INotificationService notificationService) : IStaleTaskRecoveryService
 {
+    private const string StalledActivityType = "stalled";
+
+    /// <summary>
+    /// NICHT-destruktiver Watchdog: markiert „In progress"-Tasks ohne Aktivität seit
+    /// <paramref name="stalledThreshold"/> als hängend (Activity-Event + Notification an Iris),
+    /// OHNE die Spalte zu ändern oder Arbeit zu verwerfen. Iris eskaliert dann (nachfragen,
+    /// neu delegieren, ggf. auf Blocked setzen). Dedup: bereits gemeldete Hänger werden nicht
+    /// erneut gemeldet, solange kein neuer Fortschritt (andere Activity) dazwischen liegt.
+    /// </summary>
+    public async Task<int> FlagStalledInProgressTasksAsync(TimeSpan stalledThreshold, CancellationToken ct = default)
+    {
+        var now = DateTimeOffset.UtcNow;
+        var threshold = now - stalledThreshold;
+        var allTasks = await taskRepository.GetAllAsync(ct);
+
+        var inProgress = allTasks
+            .Where(t => string.Equals(t.State, TaskStateHelper.ToStateString(TaskState.InProgress), StringComparison.OrdinalIgnoreCase))
+            .ToList();
+        if (inProgress.Count == 0)
+            return 0;
+
+        var activities = await activityRepository.GetRecentForTasksAsync(inProgress.Select(t => t.Id), ct);
+        var activityByTask = activities
+            .Where(a => a.TaskId.HasValue)
+            .GroupBy(a => a.TaskId!.Value)
+            .ToDictionary(g => g.Key, g => g.OrderByDescending(a => a.CreatedAt).ToList());
+
+        var flaggedCount = 0;
+
+        foreach (var task in inProgress)
+        {
+            activityByTask.TryGetValue(task.Id, out var taskActivity);
+            var latest = taskActivity?.FirstOrDefault();
+            var lastProgressAt = latest?.CreatedAt ?? task.UpdatedAt;
+
+            if (lastProgressAt >= threshold)
+                continue;
+
+            // Dedup: schon als hängend gemeldet und seither kein neuer Fortschritt.
+            if (latest is not null && string.Equals(latest.Type, StalledActivityType, StringComparison.OrdinalIgnoreCase))
+                continue;
+
+            var silentFor = now - lastProgressAt;
+            await activityRepository.AddAsync(new ActivityEvent
+            {
+                Type = StalledActivityType,
+                Message = $"Watchdog: keine Aktivität seit {FormatDuration(silentFor)} (Schwelle {FormatDuration(stalledThreshold)}). Task bleibt In progress, Iris zur Eskalation benachrichtigt.",
+                TaskId = task.Id
+            }, ct);
+
+            await notificationService.CreateAsync(
+                "task_stalled",
+                $"Task hängt: {task.Title}",
+                $"Seit {FormatDuration(silentFor)} keine Aktivität. Bitte nachfassen, neu delegieren oder blockieren.",
+                "iris",
+                task.Id,
+                ct);
+
+            flaggedCount++;
+        }
+
+        if (flaggedCount > 0)
+            liveUpdateService.Publish("tasks.board.snapshot", await BuildBoardSnapshotAsync(ct), "board");
+
+        return flaggedCount;
+    }
+
+    /// <summary>
+    /// Destruktiver Fallback (nur manuell via Endpoint / expliziter Cron): setzt hängende
+    /// „In progress"-Tasks hart auf Backlog zurück. Verwirft laufenden Kontext — daher NICHT
+    /// mehr der Standard-Watchdog, sondern nur noch auf Anforderung.
+    /// </summary>
     public async Task<int> ResetStaleInProgressTasksAsync(TimeSpan staleThreshold, CancellationToken ct = default)
     {
         var threshold = DateTimeOffset.UtcNow - staleThreshold;
@@ -80,88 +153,8 @@ public sealed class StaleTaskRecoveryService(
     private async Task<BoardResponse> BuildBoardSnapshotAsync(CancellationToken ct)
     {
         var allTasks = await taskRepository.GetAllAsync(ct);
-        var taskIds = allTasks.Select(task => task.Id).ToList();
-        var activity = await activityRepository.GetRecentForTasksAsync(taskIds, ct);
-
-        var backlog = new List<DashboardTaskDto>();
-        var inProgress = new List<DashboardTaskDto>();
-        var review = new List<DashboardTaskDto>();
-        var blocked = new List<DashboardTaskDto>();
-        var done = new List<DashboardTaskDto>();
-
-        foreach (var task in allTasks)
-        {
-            var dto = MapToDtoWithChildren(task, allTasks, activity);
-            switch (task.State.ToLowerInvariant())
-            {
-                case "backlog": backlog.Add(dto); break;
-                case "in progress": inProgress.Add(dto); break;
-                case "review": review.Add(dto); break;
-                case "blocked": blocked.Add(dto); break;
-                case "done": done.Add(dto); break;
-                default: backlog.Add(dto); break;
-            }
-        }
-
-        backlog.Sort(SortByPriorityThenCreatedAt);
-        inProgress.Sort(SortByPriorityThenCreatedAt);
-        review.Sort(SortByPriorityThenCreatedAt);
-        blocked.Sort(SortByPriorityThenCreatedAt);
-        done.Sort(SortByPriorityThenCreatedAt);
-
-        return new BoardResponse(backlog, inProgress, review, blocked, done);
-    }
-
-    private static DashboardTaskDto MapToDtoWithChildren(
-        WorkTask task,
-        IReadOnlyList<WorkTask> allTasks,
-        IEnumerable<ActivityEvent> activity)
-    {
-        var childTasks = allTasks
-            .Where(candidate => candidate.ParentTaskId == task.Id)
-            .OrderByDescending(candidate => candidate.UpdatedAt)
-            .ToList();
-
-        var childDtos = childTasks.Select(child => MapToDtoWithActivity(child, activity)).ToList();
-        var openChildTaskCount = childTasks.Count(child => !string.Equals(child.State, "Done", StringComparison.OrdinalIgnoreCase));
-        var dto = MapToDtoWithActivity(task, activity);
-
-        return dto with
-        {
-            ChildTasks = childDtos,
-            ChildTaskCount = childDtos.Count,
-            OpenChildTaskCount = openChildTaskCount,
-            HasVisibleDelegation = dto.ParentTaskId.HasValue || childDtos.Count > 0 || dto.IsAgentTask
-        };
-    }
-
-    private static DashboardTaskDto MapToDtoWithActivity(WorkTask task, IEnumerable<ActivityEvent> activity)
-    {
-        var last = activity
-            .Where(entry => entry.TaskId == task.Id)
-            .OrderByDescending(entry => entry.CreatedAt)
-            .FirstOrDefault();
-
-        return new DashboardTaskDto(
-            task.Id,
-            task.Title,
-            task.Detail,
-            task.Source,
-            task.State,
-            task.Priority,
-            task.AssignedTo,
-            task.ParentTaskId,
-            task.DueDate,
-            task.CreatedAt,
-            task.UpdatedAt,
-            task.IsAgentTask,
-            task.ExpectedFrom,
-            last?.Message,
-            last?.CreatedAt,
-            null,
-            0,
-            0,
-            task.ParentTaskId.HasValue || task.IsAgentTask);
+        var activity = await activityRepository.GetRecentForTasksAsync(allTasks.Select(task => task.Id), ct);
+        return TaskService.BuildMasterBoard(allTasks, activity);
     }
 
     private static string BuildActivityMessage(
@@ -190,20 +183,9 @@ public sealed class StaleTaskRecoveryService(
     }
 
     private static string FormatDuration(TimeSpan duration)
-        => duration.ToString(@"dd\.hh\:mm\:ss");
-
-    private static int SortByPriorityThenCreatedAt(DashboardTaskDto a, DashboardTaskDto b)
     {
-        var priorityCompare = PriorityScore(b.Priority).CompareTo(PriorityScore(a.Priority));
-        return priorityCompare != 0 ? priorityCompare : a.CreatedAt.CompareTo(b.CreatedAt);
+        if (duration.TotalHours >= 1)
+            return $"{(int)duration.TotalHours}h {duration.Minutes}min";
+        return $"{Math.Max(0, (int)duration.TotalMinutes)}min";
     }
-
-    private static int PriorityScore(string priority) => priority.ToLowerInvariant() switch
-    {
-        "high" => 3,
-        "medium" => 2,
-        "normal" => 2,
-        "low" => 1,
-        _ => 2
-    };
 }