add EuroCIM 2026 poster news item

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

Author: Demi-wlw

_news/announce_EuroCIM2026.md

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+---
+layout: post
+date: 2026-04-15
+inline: true
+related_posts: false
+---
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+Give a [poster](/assets/pdf/Poster__Bayesian_Supervised_Causal_Clustering.pdf) presentation at the [European Causal Inference Meeting (EuroCIM)](https://eurocim.org/oxford-2026/program/poster-abstracts.html) 2026 in Oxford.