feat(notes): notes get their own list, a day log and an Enter chain

The editor was reachable from one button that only appeared in My Day,
which is how it got forgotten. It is now a permanent sidebar entry next
to My Day and Planned, and it fills the tasks island rather than the
details pane, because a note list is content.

Inside, the date picker is gone: today sits at the top with the capture
box, older days follow as dated groups. Enter in a note saves it and
opens the next one, Shift+Enter breaks the line so notes can be several,
Backspace on an empty note deletes it and steps back up. Deleting also
has a visible hover button instead of only "clear the text and hope".
Agent-written notes carry a marker.

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

src/ClaudeDo.Ui/ViewModels/IslandsShellViewModel.cs

@@ -340,7 +340,6 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
         Lists.SelectionChanged += (_, _) => Tasks.LoadForList(Lists.SelectedList);
         Lists.SelectionChanged += (_, _) => _ = RefreshStaleWorkerCheckAsync();
         Tasks.SelectionChanged += (_, _) => Details.Bind(Tasks.SelectedTask, Tasks.SelectionSource);
-        Tasks.NotesRequested += () => Details.ShowNotes();
         Tasks.PrepRequested += () => Details.ShowPrep();
         Tasks.ErrorReported += FlashFooterError;
         Lists.ErrorReported += FlashFooterError;