Materialize now wraps admin SQL into bigquery_query('<billing>', '<inner>')
which requires the inner SQL to be BigQuery-flavor (backticked
identifiers, native function syntax). v24 migrates existing rows from
DuckDB-flavor (bq."ds"."tbl") to (`<project>.ds.tbl`) using the
configured BQ project. Idempotent on already-converted rows; logs a
warning and skips when the project isn't configured (operator can
configure + restart for retry).
