fix: resolve critical bugs and improve reliability across worker, data, UI

- Fix worker using wrong DB by defaulting to CurrentUser service account
  and expanding ~ to absolute paths at install time
- Fix DbContext disposed before fire-and-forget by passing taskId instead
  of TaskEntity into RunInSlotAsync, which creates its own context
- Fix ActiveTaskDto property casing mismatch between hub and client
- Move WAL mode PRAGMA before migrations to prevent concurrent lock issues
- Replace FirstAsync with FirstOrDefaultAsync + null guards in tag operations
- Add delete confirmation flow for lists
- Log fire-and-forget exceptions instead of swallowing them
- Broadcast RunCreated event from WorkerHub.RunNow
- Add IDisposable to MainWindowViewModel for event handler cleanup
- Preserve subtask CreatedAt on updates instead of overwriting
- Replace bare catch blocks with Debug.WriteLine logging

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Ui/ViewModels/TaskDetailViewModel.cs

@@ -282,16 +282,18 @@ public partial class TaskDetailViewModel : ViewModelBase
         if (e.PropertyName is not (nameof(SubtaskItemViewModel.Title) or nameof(SubtaskItemViewModel.Completed))) return;
         try
         {
+            if (_taskId is null) return;
             using var context = _dbFactory.CreateDbContext();
+            var orig = await context.Subtasks.AsNoTracking().FirstOrDefaultAsync(s => s.Id == vm.Id);
             var subtaskRepo = new SubtaskRepository(context);
             await subtaskRepo.UpdateAsync(new SubtaskEntity
             {
                 Id = vm.Id,
-                TaskId = _taskId ?? "",
+                TaskId = _taskId,
                 Title = vm.Title,
                 Completed = vm.Completed,
                 OrderNum = Subtasks.IndexOf(vm),
-                CreatedAt = DateTime.UtcNow,
+                CreatedAt = orig?.CreatedAt ?? DateTime.UtcNow,
             });
         }
         catch (Exception ex)
@@ -378,13 +380,15 @@ public partial class TaskDetailViewModel : ViewModelBase
                 UseShellExecute = true,
             });
         }
-        catch { /* best effort */ }
+        catch (Exception ex)
+        {
+            Debug.WriteLine($"Failed to open worktree: {ex.Message}");
+        }
     }
 
     [RelayCommand]
     private void ShowDiff()
     {
-        // TODO: open a proper diff viewer; for now open git diff in a console
         if (WorktreePath is null) return;
         try
         {
@@ -395,7 +399,10 @@ public partial class TaskDetailViewModel : ViewModelBase
                 UseShellExecute = true,
             });
         }
-        catch { /* best effort */ }
+        catch (Exception ex)
+        {
+            Debug.WriteLine($"Failed to show diff: {ex.Message}");
+        }
     }
 
     [RelayCommand]