Avoiding citation prompt hallucinating doi.org URLs

[jamesbraza]

When given the first page of A Perspective on Explanations of Molecular Prediction Models, our citation_prompt would infer:

Wellawatte, Geemi P., et al. "A Perspective on Explanations of Molecular Prediction Models." *Department of Chemistry, University of Rochester*, 2025, https://doi.org/10.xxxx. Accessed 25 Oct. 2025.

Note there are two LLM hallucinations:

1. A doi.org URL: https://doi.org/10.xxxx
2. Accessed date: Accessed 25 Oct. 2025

We don't extract the accessed date, so that's fine, but we should correct the DOI hallucination via prompting.

[Copilot]

Pull Request Overview

This PR addresses LLM hallucination issues in citation generation by adding explicit instructions to prevent fabricated DOI URLs. The change modifies the citation prompt to instruct the model not to invent DOI links when they cannot be found in the source material.

• Adds explicit instruction to avoid fabricating DOI links in citations
• Maintains existing functionality for date handling and MLA formatting