[DFL-AUDIT-152] Codex usage evidence

## Finding

**Original score:** 3/10  
**Owner:** Human  
**Priority:** P2  
**Workstream:** `codex-narrative`

## Evidence

Commit/branch hints exist; README does not explain concrete Codex contributions.

## Acceptance

Resolve the finding with reproducible evidence, or record an explicit accepted-risk decision.

Dependencies: none.