Address PR #443 R7 review (1 P3 actionable, provenance pin)

athey-2025-review.md:
- Replace generic arXiv abstract URL with a version-pinned v2 link so the
  reviewed artifact resolves to v2 (the current arXiv record now resolves
  to v3)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: igerber

docs/methodology/papers/athey-2025-review.md

@@ -2,7 +2,7 @@
 
 **Authors:** Susan Athey, Guido Imbens, Zhaonan Qu, Davide Viviano
 **Citation:** Athey, S., Imbens, G.W., Qu, Z., & Viviano, D. (2025). Triply Robust Panel Estimators. *arXiv preprint arXiv:2508.21536v2*.
-**PDF reviewed:** https://arxiv.org/abs/2508.21536 (v2)
+**PDF reviewed:** https://arxiv.org/abs/2508.21536v2 (version-pinned arXiv abstract for v2)
 **Review date:** 2026-02-08
 
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