Add AGENTS.md and CLAUDE.md files for documentation

Fiona Neillrequested to merge
docs-add-agents-and-claude-files into main

What does this MR do?

Add AGENTS.md and CLAUDE.md files for documentation

Mirrors the documentation-specific AGENTS.md and CLAUDE.md added to the GitLab and Omnibus GitLab projects (omnibus !9526).

Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com

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