add optional WFGY RAG failure map evaluation pack

[sabbellasri]

Refs #212

@onestardao this PR adds a first docs-only draft of the optional WFGY evaluation pack discussed in the issue.

Summary

This PR adds an optional docs-only evaluation pack for FinGPT RAG workflows that maps common financial QA failure patterns to the WFGY 16-problem ProblemMap.

The goal is to give FinGPT users a lightweight troubleshooting guide for real-world RAG deployments over filings, earnings calls, news, and simple tool-augmented finance workflows, without changing any core model or training code.

Changes

• Added fingpt/FinGPT_RAG/wfgy_evaluation_pack/README.md
• Linked the new pack from fingpt/FinGPT_RAG/README.md
• Linked the optional pack from the top-level README.md

What's Included

• A compact symptom -> ProblemMap -> "inspect this part of the FinGPT stack first" troubleshooting table
• A full No.1 to No.16 mapping from the WFGY taxonomy to likely FinGPT pipeline components
• Representative financial RAG failure cases covering hallucinated risk statements, retrieval drift over filings, prompt drift in multi-step financial QA, and misrouted tool or time-series calls

Notes

• This is a documentation-only contribution
• No changes were made to FinGPT model weights, training scripts, or benchmark code
• The WFGY taxonomy is used as an optional external diagnostic framework for users who want a shared vocabulary for RAG debugging

Reference

Upstream WFGY ProblemMap:
https://github.com/onestardao/WFGY/blob/main/ProblemMap/README.md