Remove pip-audit ignore for nltk PYSEC-2026-3740 once a fixed release ships #520

Summary

CI's pip-audit step ignores nltk advisory PYSEC-2026-3740 (aliases: CVE-2026-81726, GHSA-8mgp-746c-j5xp). nltk is pulled in by the rouge extra, added in #506. There is no fixed nltk release yet (latest is 3.10.3), so the audit can't be cleared by bumping the pin.

Why the ignore is safe

According to the OSV record, the advisory is a path traversal in nltk's model-artifact APIs: TransitionParser, AveragedPerceptron, PerceptronTagger, and maxent parameter APIs. It only applies when nltk's pathsec sandbox is enabled.

This repo doesn't call any of those APIs. It uses:

• nltk.sent_tokenize in RougeScorer (src/inference_endpoint/evaluation/scoring.py)
• rouge_score's Porter stemmer, reached through evaluate.load("rouge")

Switching to pysbd for sentence splitting wouldn't remove the dependency, because rouge_score itself requires nltk.

To do when a fix ships

Upstream fix: nltk/nltk#3753. When a fixed nltk release is published, or the advisory data is corrected (OSV's range currently says fixed: 3.10.3, but its description says "through 3.10.3"):

• Bump the nltk pin in the rouge extra (pyproject.toml) and run uv lock
• Remove --ignore-vuln PYSEC-2026-3740 from .github/workflows/test.yml
• Remove the matching notes in docs/DEVELOPMENT.md and AGENTS.md
• Confirm that uv run pip-audit passes with no ignores

Context: #506 (comment)