Merge task branch for: fix(worker): FailAsync-Guard untersuchen — ist Queued→Failed erreichbar/gewollt?

src/ClaudeDo.Worker/CLAUDE.md

@@ -69,7 +69,7 @@ Allowed transitions (enforced by `TaskStateService`):
 
 ```
 Idle               → Queued | Running (RunNow)
-Queued             → Running | Cancelled | Idle | Failed (runner guard)
+Queued             → Running | Cancelled | Idle | Failed (OverrideSlotService preflight gap: RunAsync can fail before StartRunningAsync is called)
 Running            → WaitingForReview (standalone success, no children)
                    | WaitingForChildren (parent with pending children)
                    | Done (planning/improvement child success) | Failed | Cancelled

src/ClaudeDo.Worker/State/TaskStateService.cs

@@ -198,6 +198,9 @@ public sealed class TaskStateService : ITaskStateService
     {
         await using (var ctx = await _dbFactory.CreateDbContextAsync(ct))
         {
+            // Queued is intentional: OverrideSlotService dispatches RunAsync before calling
+            // StartRunningAsync, so a preflight failure (list not found, worktree setup) can
+            // reach MarkFailed while the task is still Queued in the DB.
             var affected = await ctx.Tasks
                 .Where(t => t.Id == taskId &&
                     (t.Status == TaskStatus.Running || t.Status == TaskStatus.Queued))