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>

tests/ClaudeDo.Ui.Tests/ViewModels/DetailsIslandEmptyStateTests.cs

@@ -38,7 +38,7 @@ public class DetailsIslandEmptyStateTests : IDisposable
     private DetailsIslandViewModel NewDetailsVm(StubWorkerClient stub)
     {
         var factory = new TestDbFactory(NewContext);
-        return new DetailsIslandViewModel(factory, stub, new NullServiceProvider(), new StubNotesApi(), new ClaudeDo.Ui.Services.MergeCoordinator());
+        return new DetailsIslandViewModel(factory, stub, new NullServiceProvider(), new ClaudeDo.Ui.Services.MergeCoordinator());
     }
 
     [Fact]
@@ -60,17 +60,6 @@ public class DetailsIslandEmptyStateTests : IDisposable
         Assert.False(vm.IsEmptyStateVisible);
     }
 
-    [Fact]
-    public void IsEmptyStateVisible_false_in_notes_mode_even_without_a_task()
-    {
-        var vm = NewDetailsVm(new DefaultStub());
-
-        vm.ShowNotes();
-
-        Assert.True(vm.IsNotesMode);
-        Assert.Null(vm.Task);
-        Assert.False(vm.IsEmptyStateVisible);
-    }
 
     [Fact]
     public void IsEmptyStateVisible_false_in_prep_mode_even_without_a_task()