Cite research sources in notebooks

[Xmaster6y]

Summary

• add canonical bibliography entries for CKA, Information Imbalance, Othello-GPT, Circuit Insights, and PPO
• connect method and research notebooks to their related paper citations
• simplify the tutorials page so the research notebooks are presented directly through the notebook grid
• add a regression test ensuring every notebook citation key resolves to references.bib

Validation

• uv run pytest tests -q — 863 passed, 1 skipped
• uv run pre-commit run --all-files — passed
• uv run sphinx-build -W --keep-going -b html docs/source <temporary-directory> — passed

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-08T12:48:50.820647Z	b4e2881	PR opened

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.80%. Comparing base (36e3165) to head (5c82c2b).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #165   +/-   ##
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  Coverage   98.80%   98.80%           
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  Files          55       55           
  Lines        5087     5087           
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  Hits         5026     5026           
  Misses         61       61           

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[cubic-dev-ai]

No issues found across 14 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

<sub>Auto-approved: Adds bibliographic citations to notebook documentation, extends references.bib with five new entries, and adds a regression test ensuring all notebook citation keys resolve to bib keys. The change is documentation-only with a focused correctness test, clearly beneficial and bounded.

Re-trigger cubic</sub>