Reusable Testcontainers fixtures for the Culvert framework's integration tests. Provides emulator containers (BigQuery via goccy/bigquery-emulator, GCS via fsouza/fake-gcs-server) plus helpers that build GCP SDK clients pointed at those emulators. Pub/Sub uses Testcontainers' built-in PubSubEmulatorContainer directly (no wrapper needed) — see the module README. This is a TEST-SUPPORT LIBRARY: dependencies are declared in compile scope so ...