Modernize docs site UI and styling; update static HTML/CSS/JS and remove duplicate site copies

[OgeonX-Ai]

Motivation

• Improve the static documentation pages to a modern, enterprise-ready look and improve usability across the site.
• Keep a single canonical static site location under docs/index.html and remove duplicate copies to avoid stale content.
• Align repository instructions so the docs UX expectation is documented and continuously refinable.

Description

• Redesigned the site layout and content blocks by updating the HTML pages under docs/index.html and docs/pages/* to a topbar + sidebar + content layout.
• Replaced the stylesheet with a modern, enterprise docs/assets/style.css and refreshed visual tokens (colors, spacing, shadows, pills, cards).
• Refactored navigation script docs/assets/app.js to use createNavLink() and nav-link classes and preserved simple JS search across pages.
• Removed duplicate static site copies (docs/site/ and site/) and updated README.md and CODEX_INSTRUCTIONS.md to reference docs/index.html and to call out continuous UX refinement.

Testing

• Served the docs/ directory with python -m http.server and ran a Playwright script to capture a screenshot at artifacts/docs-index.png, which completed successfully.
• No repository CI/linters were executed as part of this change; static HTML/CSS updates were validated locally only.

---

Codex Task