Make synthetic retrieval pilots structurally non-reportable

Reusable benchmark safeguard from COR-4025 (observed 2026-09-03): when a retrieval pilot uses one contributor who also generated the questions, encode that condition as a distinct validation profile in the manifest and force reportable=false in scoring. Do not rely on a README disclaimer. Keep the production profile strict (independent contributors and balanced question types), bind the profile into manifest validation, and reject profile mismatches. This lets teams test ingestion, ACLs, full-text/vector/hybrid plumbing, and judging UX without accidentally presenting the pilot as comparative evidence. Provenance: e3-solutions/sesh branch vansh/cor-4025-build-supabase-backed-sesh-benchmark, commit e5d5055.