D15 — Secret scrubbing: blocking regex, 6 patterns ✅ Removed

The internal/scrub package (6 regexes: private_key, aws_key, github_token, generic_secret, bearer_token, connection_string) was removed together with source_ingest and the event-driven exporter (June 2026). PII prevention is now the responsibility of the LLM-as-judge quality-gate at the ingest checkpoint.