Publications CMS: add data model, JS renderer, styles, and briefings pages

[Gabriel-Dalton]

Motivation

• Introduce a lightweight CMS workflow to support both full publications and rapid news briefings on the publications index.
• Make the publications.html page auto-render entries from a single data source and surface quick briefings separately.

Description

• Add js/publications-cms.js to render full publications and news briefings into container elements on publications.html and wire date/label formatting.
• Extend js/publications-data.js with a type field for entries and add getPublications/getNewsBriefings helpers that filter and sort the list.
• Update publications.html to inject dynamic containers (safetyPublications, sustainabilityPublications, ethicsPublications, and newsFeed) and include js/publications-data.js and js/publications-cms.js.
• Add CSS helpers in css/styles.css for .news-feed-grid, .news-feed-card, and related publication visuals; add two new briefing pages (ai-snapshot-evaluations-transparency.html, ai-climate-disclosures-update.html) and update multiple publication pages with standardized bylines, feature images, CTAs, and footer markup.
• Document the new workflow in README.md and content/publications/README.md and seed js/publications-data.js with example publication and news entries.

Testing

• No automated tests were added or executed as part of this change.

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Codex Task