Function cmd_gate 

pub fn cmd_gate(args: &GateArgs) -> i32

One enforcement entry point: validation + relationships + review under the corpus policy. Blocking findings fail (exit 1); a malformed .decided/config.yaml is an operational error — decided: <message>, exit 1 (NOT the exit-2 usage class). The not-a-directory check runs BEFORE the config load, so a bad path wins exit 2 even beside a malformed config.