Add NOTICE crediting upstream vvaharnessVerified

The methodology and the gate/lens prompt text are adapted (in places
verbatim) from vvaharness (Copyright 2026 Visa, Inc., Apache-2.0). The
skill sources stay free of upstream references; NOTICE is the canonical
record of that lineage, as Apache-2.0 attribution requires.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>