Arc: DuckDB I/O aliases bypass database RBAC after CVE-2026-47735

Summary The fix for CVE-2026-47735 released 2026.06.1 is incomplete. It added a DuckDB sandbox SET GLOBAL alloweddirectories=; SET GLOBAL enableexternalaccess=false and an Arc SQL-layer denylist of the literal functions readparquet and arcpartitionagg. The sandbox correctly blocks reads outside t...