Docs: add WFGY 16-problem checklist as RAG troubleshooting reference (langgenius/dify#32439)

[onestardao]

This PR implements the documentation part of langgenius/dify#32439.

Changes:

• Adds a short “Troubleshoot RAG quality” section to the Knowledge overview page.
• Briefly introduces the 4 regions and 16 common failure patterns (input/retrieval, reasoning/planning, state/context, infra/deployment).
• Adds an external “Read More” link to the open-source WFGY ProblemMap (16 real-world RAG failure modes and suggested fixes).

No product or API changes are included in this PR.
The checklist is optional and can be used as a shared vocabulary when debugging RAG pipelines in Dify.

[dosubot]

Related Documentation

Checked 0 published document(s) in 2 knowledge base(s). No updates required.

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[RiskeyL]

Hi @onestardao, thank you for the contribution! After reviewing, we're going to pass on this PR. The added section introduces an external framework and terminology that aren't part of Dify, and the troubleshooting advice doesn't connect to any specific Dify feature or workflow. Our docs focus on helping users work with Dify's own tools and capabilities.

For sharing this kind of resource, community channels like forums, social media, or curated awesome-lists tend to be a better fit than product documentation. Thanks for your interest in Dify!