Remediate the 2026-09-03 feature-test findings

plugins/guides/api/routes.py

@@ -503,8 +503,19 @@ def restore_revision(guideid, revisionid):
                               'You do not have permission to edit this guide',
                               http_code=403)
 
+    before = guide.revision
     authoring.restore(guide, revision, userid=_userid())
     db.session.commit()
+
+    # save() dedups on the content hash, so restoring the version that is
+    # already current writes nothing. Saying "Restored version N as a new draft
+    # version" in that case describes a revision that does not exist - and the
+    # revision list, unchanged, quietly disagrees with the message.
+    if guide.revision == before:
+        return success_response(
+            guide.to_dict(includeblocks=True),
+            message='Version {} is already the current content, so nothing '
+                    'changed'.format(revision.revision))
     return success_response(guide.to_dict(includeblocks=True),
                             message='Restored version {} as a new draft version'
                                     .format(revision.revision))