Pull Request resolves #40641 .

• I read the Generative AI policy and my contribution is either not created with the help of AI or is compatible with the policy and GNU/GPL 2 or later.

Summary of Changes

This fixes an issue where the CodeMirror editor is duplicated when subform rows are reordered as it adds a minimal guard using the JoomlaEditor registry to prevent duplicate initialization

Testing Instructions

1. Set CodeMirror as the default editor
2. Create or edit an item that contains a subform field with an editor field
3. Go to articles -> new -> feilds and add multiple subform rows
4. Drag and reorder the rows

Actual result BEFORE applying this Pull Request

Each time a subform row is reordered, a new CodeMirror editor instance is created for the same textarea, resulting in duplicated editors in the ui

Expected result AFTER applying this Pull Request

The CodeMirror editor is initialized only once per textarea

Link to documentations

Please select:

• Documentation link for guide.joomla.org:

• No documentation changes for guide.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed