refactor: remove unnecessary Fragment wrapping

[TrevorBurnham]

Description

Children.only() already validates that the highlight result is a single element. Wrapping that result in a Fragment first, only to read .props.children back off the wrapper, is a no-op:

-  const codeElementWrapper: ReactElement = createElement(Fragment, null, code);
-  const codeElement = Children.only(codeElementWrapper.props.children);
+  const codeElement = Children.only(code) as ReactElement;

The Children.only() call is kept deliberately. CodeViewProps.highlight is typed (code: string) => React.ReactNode, so a consumer can return a string, an array, or a fragment. Children.only() turns those cases into a clear error rather than silently rendering nothing when the render path reads codeElement.props.children. The old code got its ReactElement typing implicitly from the Fragment wrapper, so the explicit cast replaces that.

No behavior change.

How has this been tested?

Existing unit tests pass (51 tests). Type-checked, linted, and verified in the dev server that the demos render unchanged.

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[pan-kot]

The changes conflict with main.

[TrevorBurnham]

@pan-kot Updated!