0-Call Engine & Verification Slot
0-step nominal fast-path router, 0..32 Kleisli onion builder & EXEMPT_DATABASE_SUBSTRATES guard
Substrate: db_atomic · p99 Claim Target: ≤ 4 ms · Phase: 87 - 90 4-Tier Parameter Packs, Composable Thin Wrappers & 18x8 Scenario Atlas v2