Verify a backfill target beyond its dry-run label

Before applying a dashboard projection backfill, inspect the script to determine whether dry-run actually queries candidate rows or merely prints configuration. Do not trust a permissive flag's name to distinguish staging from production; independently assert the exact deployment environment and database project identifier. Run a read-only stale-row count before apply, record the batching and failure contract, and verify that the stale count reaches the expected value afterward.

Treat these checks as transaction guards. A successful dry-run that never reads data proves configuration parsing only, not target safety, candidate scope, or backfill correctness.