CVE-2026-47735: Arc has an authenticated arbitrary local-file read via DuckDB I/O functions that bypasses RBAC table-level checks

Arc’s user-SQL validator (internal/api/query.go:ValidateSQLRequest) blocked only read_parquet( and arc_partition_agg( via regex denylist. The broader DuckDB I/O function family — read_csv_auto, read_csv, read_json, read_json_auto, read_text, read_blob, glob, parquet_metadata, parquet_schema, read_xlsx, etc. — was not blocked. RBAC table-reference extraction inspected only FROM/JOIN clauses, so scalar table functions in the SELECT list slipped past both layers.