[Need support]: Document the 2-hop sample data and eval harness

[TKaltofen]

What and why

demo/data/README.md documents the sample data files, but the 2-hop assets are missing: sample_qa_2hop.txt exists in the directory and demo/eval_qa_accuracy_2hop.py consumes it, yet neither is mentioned anywhere in the markdown docs. A reader browsing the data folder cannot tell what the file is for or how it differs from sample_qa.txt.

Pointers

• demo/data/README.md ("Files" section)
• demo/data/sample_qa_2hop.txt
• demo/eval_qa_accuracy_2hop.py

Steps

1. Add a bullet for sample_qa_2hop.txt to the "Files" section, describing its format and that it holds 2-hop question/answer pairs.
2. Mention eval_qa_accuracy_2hop.py where the README discusses running the QA accuracy demo (including the full-MetaQA instructions if the 2-hop split applies there too).
3. Run tox.

Acceptance criteria

• The README documents every committed file in demo/data/.
• The 2-hop eval harness is discoverable from the data README.

Notes

This project uses semantic versioning driven by Conventional Commits, so the PR title matters: use docs: document 2-hop sample data and eval harness.

New to the project? This issue is a good entry point, we are happy to help in the comments.

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