verify(P3): dead-code-and-stale-prefix-cleanup — 4-layer verify PASS + ship

VERIFY: structural — dead export + stale comments + prefixes gone; behavioral — 616 tests + CI PASS; quality — env-override test updated.

---ci---
project: acdl
phase: 3
milestone: v1.16
status: complete
phase_role: execution
requirements:
  covered: [REQ-167]
  partial: []
---/ci---

scripts/run_regression.sh

@@ -19,7 +19,7 @@ ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
 cd "$ROOT"
 
 echo "=== Nova Regression VERIFY (D-091) ==="
-# Dual-read: NOVA_* preferred, ACDL_* fallback (removed in P5).
+# NOVA_* env vars only (ACDL_* fallback removed in v1.15 P5, REQ-164).
 echo "milestone: ${NOVA_REGRESSION_MILESTONE:-v1.10}  phase: ${NOVA_REGRESSION_PHASE:-52}"
 echo ""