feat(attedit): show attribute prompts in the editor

Each row in the attribute editor now shows the attribute's prompt — the
text defined on the block's ATTDEF — falling back to the tag when the
block defines no prompt. The prompt is read from the block definition,
since attribute instances carry only tag + value.

Bumps the acadrust pin to pull the matching reader fix: its DWG object
reader was discarding the ATTDEF prompt, so every prompt came back empty.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/app/update/mod.rs

@@ -2270,7 +2270,7 @@ impl OpenCADStudio {
             }
             Message::AttrEditorInput { idx, value } => {
                 if let Some(field) = self.attr_editor_fields.get_mut(idx) {
-                    field.1 = value;
+                    field.2 = value;
                 }
                 Task::none()
             }