fix(worker): fail the task when a queue slot runner throws

RunInSlotAsync only logged an unexpected exception, leaving a task stuck
Running in the DB forever with the UI never notified (the raw-SQL queue
claim that put it there never broadcasts). Cancellation is handled
separately and left alone, since the cancel path already wrote the
terminal status.

src/ClaudeDo.Worker/Queue/QueueService.cs

@@ -343,9 +343,28 @@ public sealed class QueueService : BackgroundService
 
             await _runner.RunAsync(task, "queue", ct, alreadyClaimed: true);
         }
+        catch (OperationCanceledException)
+        {
+            // Cancellation is driven by the cancel path, which already wrote the terminal status.
+            // Marking the task Failed here would be a regression (it would stomp Cancelled).
+            _logger.LogInformation("Slot runner cancelled for task {TaskId}", taskId);
+        }
         catch (Exception ex)
         {
             _logger.LogError(ex, "Slot runner error for task {TaskId}", taskId);
+
+            // The picker already committed status='running' before this ran. Without this the
+            // task stays Running forever and the UI never hears about it — it keeps showing the
+            // pre-claim status because the raw-SQL claim itself never broadcasts.
+            try
+            {
+                await _state.FailAsync(taskId, DateTime.UtcNow,
+                    $"Slot runner error: {ex.Message}", CancellationToken.None);
+            }
+            catch (Exception failEx)
+            {
+                _logger.LogError(failEx, "Could not mark task {TaskId} as failed after a slot error", taskId);
+            }
         }
     }
 }