Fix KCard area not taking available width

[MisRob]

Description

Fixes the issue that @akolson discovered in Studio when cards didn't take the full available width.

Issue addressed

A bug discovered in learningequality/studio#4803

Before/after screenshots

Before	After

Changelog

• Description: Fixes KCard area not taking available width
• Products impact: bugfix
• Addresses: A bug discovered in Implement recommendations display studio#4803
• Components: KCard
• Breaking: no
• Impacts a11y: no
• Guidance: -

Steps to test

I linked to Studio.

Implementation notes

At a high level, how did you implement this?

Cause: Even though the wrapping <li> had the correct width, its child <div class="card-area" ...> didn't take the full width of its parent.

This PR fixes it by setting 100% width on the div.

Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical and brittle code paths are covered by unit tests
• The change is described in the changelog section above

Reviewer guidance

• Is the code clean and well-commented?
• Are there tests for this change?
• Are all UI components LTR and RTL compliant (if applicable)?
• Add other things to check for here

Comments

Note that the thumbnail overflow will be resolved in another PR.

[akolson]

Thanks @MisRob! This fixes the bug. The changes LGTM!