fix(insert): attribute grips follow ATTMODE 2 and annotative scale

Follow-up to the block-attribute grips picked from #1386.

- Movability no longer includes the invisible flag: an attribute ATTMODE 2
  displays is grippable, so the grip the display-aware list shows can be
  dragged. The document-less grips() still skips invisible attributes,
  since it cannot consult ATTMODE.
- The grip sits on the displayed attribute, which an annotative insert
  scales about its insertion point; Scene::apply_grip now unscales the
  dragged target the same way before the attribute stores it, so the grip
  no longer jumps to twice the drag at scale 2.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

src/scene/modify.rs

@@ -1443,6 +1443,17 @@ impl Scene {
         if self.is_layer_locked(handle) {
             return;
         }
+        // An attribute grip sits on the displayed (annotation-scaled)
+        // attribute; the stored one is unscaled.
+        let apply = match self.document.get_entity(handle) {
+            Some(EntityType::Insert(insert)) => crate::entities::insert::unscale_attribute_grip(
+                insert,
+                self.annotation_scale,
+                grip_id,
+                apply,
+            ),
+            _ => apply,
+        };
         if self.apply_solid_history_grip(handle, grip_id, apply.clone()) {
             return;
         }