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/Views/Islands/TasksIslandView.axaml

@@ -68,7 +68,8 @@
     </Border>
 
     <!-- Add-task row -->
-    <Border DockPanel.Dock="Top" Classes="add-task" Margin="16,14,16,8">
+    <Border DockPanel.Dock="Top" Classes="add-task" Margin="16,14,16,8"
+            IsVisible="{Binding !IsNotesList}">
       <Grid ColumnDefinitions="Auto,*,Auto">
         <Border Grid.Column="0" Classes="add-task-plus" VerticalAlignment="Center">
           <PathIcon Width="12" Height="12" Data="{StaticResource Icon.Plus}"
@@ -90,14 +91,6 @@
       </Grid>
     </Border>
 
-    <!-- Notes pinned row (My Day only) -->
-    <Button DockPanel.Dock="Top"
-            Classes="btn" HorizontalAlignment="Stretch" HorizontalContentAlignment="Left"
-            Margin="16,0,16,8"
-            IsVisible="{Binding ShowNotesRow}"
-            Command="{Binding OpenNotesCommand}"
-            Content="{loc:Tr tasks.notesPinnedRow}"/>
-
     <!-- Task list: one flat, virtualized ListBox. Rows is HeaderRow | TaskRowViewModel — group
          headers are regular entries, not a separate ItemsControl per section, so a
          VirtualizingStackPanel actually bounds the realized container count.
@@ -106,6 +99,7 @@
          unreachable. -->
     <Panel>
       <ListBox x:Name="RowsListBox"
+               IsVisible="{Binding !IsNotesList}"
                ItemsSource="{Binding Rows}"
                Background="Transparent"
                BorderThickness="0">
@@ -172,6 +166,11 @@
                    Foreground="{DynamicResource TextMuteBrush}"
                    TextAlignment="Center" TextWrapping="Wrap"/>
       </StackPanel>
+
+      <!-- The notes list is not a task list: same island slot, different content. -->
+      <Panel IsVisible="{Binding IsNotesList}">
+        <islands:NotesEditorView DataContext="{Binding Notes}"/>
+      </Panel>
     </Panel>
 
   </DockPanel>