View mode does not persist on validation errors

Problem/Motivation

I've separate view mode for preview, but same_page_preview hardcodes to "full" view mode on javascript https://git.drupalcode.org/project/same_page_preview/-/blob/2.1.x/js/sam...

Steps to reproduce

1. Install Drupal 11.x and same_page_preview module
2. Make some field required (eg. /admin/structure/types/manage/article/fields/node.article.field_tags)
3. Create content (/node/add/article)
4. Launch preview and select "teaser" view mode
5. Edit text body area and make sure tags field is empty.
6. Validation error is printed on FULL view mode

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes