fix: ambiguous column name in content-change JOIN query

news_mcp/jobs/poller.py

@@ -179,7 +179,7 @@ class ClusterPoller:
             with self.store._conn() as conn:
                 for ak in changed_keys:
                     row = conn.execute(
-                        "SELECT cluster_id, payload FROM seen_articles sa "
+                        "SELECT sa.cluster_id, c.payload FROM seen_articles sa "
                         "JOIN clusters c ON c.cluster_id = sa.cluster_id "
                         "WHERE sa.article_key=?",
                         (ak,),