The proef API engine: [EngineFactory]/[EngineSession] over embedded hurl
(ADR-0001).
hurl's crates are pinned exactly (=8.0.1) and built --locked — the crates
break API in minor releases; upgrades go only through the canary + runbook
(ADR-0003, IMPLEMENTATION-PLAN §7).
The engine claims the hurl step kind, contributes doctor checks, and
executes scenario artifacts via the embedded run_entries (see the
session module source for the adapter mechanics).