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/DetailsIslandResetAndRetryTests.cs

@@ -48,7 +48,7 @@ public class DetailsIslandResetAndRetryTests : IDisposable
     {
         var factory = new TestDbFactory(NewContext);
         return new DetailsIslandViewModel(
-            factory, worker, new NullServiceProvider(), new StubNotesApi(), new ClaudeDo.Ui.Services.MergeCoordinator());
+            factory, worker, new NullServiceProvider(), new ClaudeDo.Ui.Services.MergeCoordinator());
     }
 
     [Fact]