Layout builder issues

Problem/Motivation

There are numerous issues with Layout Builder UI:

1. "Move" action in Drupal layouts throws an error in the AJAX response, Because it can’t find the ThreeColumnsLayout, which is referenced in the civictheme.layouts.yml file.

   Commenting out this line https://github.com/civictheme/monorepo-drupal/blob/develop/web/themes/co... and a `drush cr` allows the layouts sidebar to render, but (I assume) the actions provided by that class are not being applied.

2. Off canvas menu - multi-value widget is printing a stray `>`
3. Cannot drag and drop blocks
4. Context menu has bugs in rendering

Acceptance criteria

AC 1 - Move
Given I'm a Site Administrator
And a page is open in Layout Builder edit mode
When I use the "Move" action on a layout block or section
Then the action completes successfully
And no AJAX or JavaScript errors occur

AC 2 - Sidebar
Given I'm a Site Administrator
And the Layout Builder sidebar is visible
When layouts are listed
Then all layouts render correctly
And no layout-related errors are logged

AC 3 - Off canvas menu - multi-value widget is printing a stray `>`
Given I'm a Site Administrator
And the off-canvas editing panel is open
When a multi-value field widget is displayed
Then no stray characters are visible
And the widget renders correctly

AC 4 - Drag and drop
Given I'm a Site Administrator
And a page is in Layout Builder edit mode
When the user drags a block to a new position
Then the block can be repositioned successfully
And the new order is saved

AC 5 - Context menu rendering issues
Given I'm a Site Administrator
And a page is open in Layout Builder edit mode
When the context menu is opened on a block or section
Then the menu renders correctly
And all actions are visible