Set up agentic workflows to keep documentation healthy

## Summary

As we improve the repository documentation structure, we should also establish agentic workflows that help keep docs healthy over time.

## Focus

- Use coding agents to help identify stale documentation paths, missing cross-links, and areas that lack clear ownership
- Establish lightweight maintenance routines for documentation health
- Make it easier to catch drift between the codebase and the docs surface
- Support a more regular cadence of documentation cleanup and improvement

## Outcomes

- Documentation stays easier to navigate over time
- Common documentation issues are identified earlier
- Contributors have clearer signals when docs need attention
- The long-term docs architecture remains healthier as the repo evolves

Parent issue: #7164