feat(field): table formula buttons, block placeholders, attribute fields on insert, plot-time field stamping

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/app/command_driver/entity_commit.rs

@@ -231,7 +231,15 @@ impl OpenCADStudio {
         // objects are not part of the add delta, so the step is a snapshot.
         let text_field = self.tabs[i].active_cmd.as_ref().and_then(|cmd| cmd.text_field());
         let label = self.history_label_from_active_cmd(i, "ENTITY");
-        let delta_safe = text_field.is_none() && self.delta_add_safe(i, &entity);
+        // A block reference whose attribute definitions carry fields gets
+        // them copied onto its attributes (field objects: snapshot step).
+        let attribute_fields = match &entity {
+            codec::EntityType::Insert(insert) if !insert.attributes.is_empty() => {
+                crate::entities::field::block_has_attribute_fields(&self.tabs[i].scene.document, &insert.block_name)
+            }
+            _ => false,
+        };
+        let delta_safe = text_field.is_none() && !attribute_fields && self.delta_add_safe(i, &entity);
         let field_value = match &entity {
             codec::EntityType::MText(m) => m.value.clone(),
             codec::EntityType::AttributeDefinition(a) => a.default_value.clone(),
@@ -264,6 +272,10 @@ impl OpenCADStudio {
                 &field_value,
             );
         }
+        if let (Some(handle), true) = (committed, attribute_fields) {
+            crate::entities::field::attach_attribute_fields(&mut self.tabs[i].scene.document, handle);
+            self.tabs[i].scene.bump_entities(&[(handle, crate::scene::ChangeKind::Modified)]);
+        }
         if let Some(handle) = committed {
             self.apply_continuous_constraints(i, &[handle]);
         }