What

Part of #315.

Adds structural assertions to jsx-parser tests that verify the parser produces correct React element output.

Why

PR #331 covered 10 React components in blocks-v3. For most, the mocks were sufficient to test rendered output. But jsx-parser is different: it parses HTML strings into React elements using jQuery DOM methods. The simple jQuery mock in #331 didn't support these, so tests could only verify the parser runs without errors.

This PR enhances the mock to return real DOM nodes, enabling assertions on what the parser actually produces.

How

Enhanced the jQuery mock to parse HTML using DOMParser, enabling assertions on actual output:

const result = parseJSX( '<div class="my-class">Hello</div>' );
expect( result.type ).toBe( 'div' );
expect( result.props.className ).toBe( 'my-class' );
expect( result.props.children ).toBe( 'Hello' );

Testing Instructions

npm run test:unit -- tests/js/blocks-v3/
# 174 tests pass