feat(tasks): mark tasks and lists as manual

Reminders written down as todos had no home: every task looked like Claude work.
A manual task now shows a MANUAL badge and hides send-to-queue, refine and the
planning session; the queue picker, daily prep and the list handler all skip it,
with a TaskStateService guard so the MCP surface and hub cannot start one either.
Opening a hand-driven ConPTY session stays available on purpose.

A list can be marked manual in its settings, which makes tasks created there
(UI and MCP add_task) start out manual. Toggle per task from its context menu.

src/ClaudeDo.Ui/ViewModels/Modals/MergeHelperSelectionModalViewModel.cs

@@ -56,6 +56,8 @@ public sealed partial class MergeHelperSelectionModalViewModel : ViewModelBase
         var candidates = await ctx.Tasks.AsNoTracking()
             .Where(t => t.Status != TaskStatus.Done && t.Status != TaskStatus.Cancelled)
             .Where(t => t.ListId == _listId)
+            // Manual tasks are reminders the user owns — never offer them to the handler.
+            .Where(t => !t.IsManual)
             .OrderBy(t => t.SortOrder).ThenBy(t => t.CreatedAt)
             .Select(t => new { t.Id, t.Title, t.Status })
             .ToListAsync(ct);