Pull Request resolves #47292 .

• 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

In the Mail Templates edit view com_mails, there are two editor fields: a plain text "Body" field and a rich text "HTML Body" field.

Previously, the plain text <textarea> (and the HTML Body <textarea> when the editor is toggled off) had no explicit width defined. This caused them to fall back to the browser's default narrow cols behavior, leaving them much narrower than their Bootstrap col-md-9 container and creating layout inconsistency.

This PR adds the width="100%" attribute to both the body and htmlbody fields in the com_mails (template.xml)(file:administrator/components/com_mails/forms/template.xml) form definition. Joomla's [EditorField (file:libraries/src/Form/Field/EditorField.php) safely parses this string attribute and passes it to the editor plugins (None, TinyMCE, CodeMirror), which apply it as an inline style="width: 100%;" to ensure the text areas expand gracefully to fill their containers.

Testing Instructions

1. Log into the Joomla Administrator backend.
2. Navigate to System -> Mail Templates.
3. Open any Mail Template for editing (e.g., "User Actions Log").
4. Test the Plain Text Body field: Verify that the textarea of the "Body" field is now full width (100% of the available column space).
5. Test the HTML Body Toggle: Scroll down to the "HTML Body" field. Click the Toggle Editor button below the editor to switch to the raw HTML text view. Verify that the revealed textarea is also full width and does not shrink to a narrow column constraint.

Actual result BEFORE applying this Pull Request

Expected result AFTER applying this Pull Request

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