testimonial is a composition over section, with a codemod for its byline

Acceptance Criteria

• A composed testimonial definition, per SPEC-161 D1's sketch, places one section with media-position="start" and media="portrait", with no {% if %}
• It declares defaults: { elevation: flat, density: compact }, and renders a surface and the round avatar for every variant
• variant is a declared attribute emitted as data-variant on the root
• The byline renders through the lead layout (WORK-667), with the author name as lead and the role visible at compact density
• Its JSON-LD matches the plugin's Review graph (reviewBody, Person author, Rating) at both harvest points, compared against the SEO baseline rather than re-recorded
• A codemod rewrites **Name** — Role paragraphs into author and role attributes, using the plugin's own parser, and is run over this repository's content
• A page still written the old way reports content-unmatched at error severity rather than rendering the paragraph
• Rendered beside the plugin testimonial for every gallery fixture; every difference is listed and explained
• The plugin testimonial is unchanged; replacing it is a later step