fix(mirror): a mirrored dimension keeps its text readable

The dimension's own block parts were mirrored with their text, so the
measurement read backwards. Text orientation is kept under reflection,
the same as TEXT and MTEXT with MIRRTEXT off.

Fixes #1639

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

src/scene/modify.rs

@@ -107,6 +107,18 @@ fn mirror_true_text_flags(e: &mut EntityType) {
     }
 }
 
+/// Transform one entity of a dimension's `*D` block. Its text reads the
+/// right way after a mirror, whatever MIRRTEXT says.
+fn transform_dimension_part(entity: &mut EntityType, t: &EntityTransform) {
+    let orient = matches!(t, EntityTransform::Mirror { .. })
+        .then(|| capture_text_orient(entity))
+        .flatten();
+    view::dispatch::apply_transform(entity, t);
+    if let Some(orient) = orient {
+        restore_text_orient(entity, &orient);
+    }
+}
+
 impl Scene {
     pub(crate) fn sync_displayed_annotation_context(&mut self, handle: Handle) -> bool {
         let scale = self.displayed_annotation_scale_handle();
@@ -357,7 +369,7 @@ impl Scene {
                 self.record_undo_before(*h, before);
             }
             if let Some(entity) = self.document.get_entity_mut(*h) {
-                view::dispatch::apply_transform(entity, t);
+                transform_dimension_part(entity, t);
             }
         }
         // The moved `*D` contents are a block definition the block cache holds;
@@ -639,7 +651,7 @@ impl Scene {
             .ok()?;
         for sub in subs {
             let mut sub = sub.clone();
-            view::dispatch::apply_transform(&mut sub, t);
+            transform_dimension_part(&mut sub, t);
             Self::reset_clone_subhandles(&mut self.document, &mut sub);
             sub.common_mut().handle = Handle::NULL;
             sub.common_mut().owner_handle = br_handle;