fix(content): publish article on asdecided.com

[tcballard]

Correction

Moves the canonical AGENTS.md Is Not a Decision System article from the documentation knowledge base to the actual AsDecided product site.

Changes

• adds the canonical article at /articles/agents-md-is-not-a-decision-system;
• adds article-specific metadata, canonical URL, Open Graph data and TechArticle JSON-LD;
• adds main-site article styling;
• links the article from the main AsDecided homepage and footer;
• adds sitemap.xml and robots.txt routes for asdecided.com;
• corrects the root metadata base from the GitHub Pages hostname to https://asdecided.com;
• removes the duplicate article, navigation item and homepage promotion from the documentation site.

The single canonical URL is now:

https://asdecided.com/articles/agents-md-is-not-a-decision-system