feat(daily-prep): trigger planning from inside the prep-log window with an empty-state hint

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ClaudeDo.Ui/Views/Islands/TasksIslandView.axaml

@@ -79,14 +79,6 @@
             Command="{Binding OpenNotesCommand}"
             Content="{loc:Tr tasks.notesPinnedRow}"/>
 
-    <!-- Prepare Day button (My Day only) -->
-    <Button DockPanel.Dock="Top"
-            Classes="btn" HorizontalAlignment="Stretch" HorizontalContentAlignment="Left"
-            Margin="16,0,16,8"
-            IsVisible="{Binding IsMyDayList}"
-            Command="{Binding PrepareDayCommand}"
-            Content="{loc:Tr tasks.prepareDay}"/>
-
     <!-- Task list -->
     <ScrollViewer>
       <StackPanel Margin="10,4">