Move homogeneous saved Scenario selections as a group

crates/oa-desktop/src/behavior/scenario/workspace.rs

@@ -144,10 +144,14 @@ pub fn view<'a>(app: &'a App, owner: Id, out: Column<'a, Message>) -> Element<'a
             && !app.source_rename.open()
             && keyboard
             && matches!(context.representation, Representation::Saved { .. }))
-        .then_some(spacing::Stamp {
-            context,
-            camera_epoch: app.camera_epoch,
-        });
+        .then(|| {
+            snapshot.as_ref().map(|snapshot| spacing::Stamp {
+                context,
+                camera_epoch: app.camera_epoch,
+                selection_generation: snapshot.generation(),
+            })
+        })
+        .flatten();
         scene.coordinate_input = capabilities.coordinate_input;
         scene.pending_placement = coordinate_input
             .then(|| state.pending_placement(owner))
@@ -162,6 +166,11 @@ pub fn view<'a>(app: &'a App, owner: Id, out: Column<'a, Message>) -> Element<'a
         let mut layers = iced::widget::stack![raw_canvas];
         if let Some(paint) = &preview {
             let feedback = spacing_feedback(p, paint.refusal, paint.diagnostics);
+            let feedback = if paint.selected_count > 1 {
+                format!("{} selected - {feedback}", paint.selected_count)
+            } else {
+                feedback
+            };
             layers = layers.push(
                 container(
                     container(text(feedback).size(12))