feat(ui,worker): surface task numbers in row/detail UI and worker log

Slice 4/5 of task-numbers: TaskRowViewModel.Number renders as a dimmed
"#123" before the row title; DetailsIslandViewModel.TaskIdBadge now
shows "#123" instead of the unusable "#T<guid-prefix>" handle; and the
curated WorkerLog business events in TaskRunner, TaskMergeService, and
TaskResetService prefix their quoted title with "#<Number>".

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

@@ -66,14 +66,18 @@
         <!-- Title + chip row + live tail -->
         <StackPanel Grid.Column="3" Spacing="6" VerticalAlignment="Center">
           <Grid ColumnDefinitions="*,Auto" VerticalAlignment="Center">
-            <TextBlock Grid.Column="0"
-                       Classes="task-title"
-                       Text="{Binding Title}" FontSize="{StaticResource FontSizeTaskTitle}"
-                       Foreground="{DynamicResource TextBrush}"
-                       TextWrapping="Wrap"
-                       FontStyle="{Binding IsDraft, Converter={StaticResource BoolToItalic}}"
-                       Opacity="{Binding IsDraft, Converter={StaticResource BoolToDraftOpacity}}"
-                       TextDecorations="{Binding Done, Converter={StaticResource StrikeIfTrue}}"/>
+            <Grid Grid.Column="0" ColumnDefinitions="Auto,*" VerticalAlignment="Center">
+              <TextBlock Grid.Column="0" Classes="meta" Text="{Binding Number, StringFormat='#{0}'}"
+                         VerticalAlignment="Center" Margin="0,0,6,0"/>
+              <TextBlock Grid.Column="1"
+                         Classes="task-title"
+                         Text="{Binding Title}" FontSize="{StaticResource FontSizeTaskTitle}"
+                         Foreground="{DynamicResource TextBrush}"
+                         TextWrapping="Wrap"
+                         FontStyle="{Binding IsDraft, Converter={StaticResource BoolToItalic}}"
+                         Opacity="{Binding IsDraft, Converter={StaticResource BoolToDraftOpacity}}"
+                         TextDecorations="{Binding Done, Converter={StaticResource StrikeIfTrue}}"/>
+            </Grid>
 
             <!-- Badges: DRAFT and planning session -->
             <StackPanel Grid.Column="1" Orientation="Horizontal" Spacing="4"