Kill switch and guardrails

qkt-guardrails is an engine-independent equity watchdog. It holds the guardian token: it can read everything, and it can stop new exposure. It cannot place orders. The switch lives in the gateway, not in qkt, so it works while qkt is down.

G="Authorization: Bearer $GATEWAY_GUARDIAN_TOKEN"
curl -H "$G" -X POST http://127.0.0.1:8443/v1/kill -d '{"scope":"all"}'
curl -H "$G" -X POST http://127.0.0.1:8443/v1/kill -d '{"scope":"symbols","symbols":["BTC_USDC-PERPETUAL"]}'
curl -H "$G" -X POST http://127.0.0.1:8443/v1/kill/release -d '{"scope":"all"}'

While the switch is on, only cancels, position closes and orders that reduce a position go through. Everything else is 423 kill_switch. The switch survives restarts.

Every change that moves it is a kill event on /v1/stream, carrying the switch as /v1/health reports it, so qkt hears it flip in order with fills.

Two tokens, two roles

Token	Variable	Can
Trader	GATEWAY_TRADER_TOKEN	Read, place, change and cancel orders, close positions. qkt uses this
Guardian	GATEWAY_GUARDIAN_TOKEN	Read, and flip the kill switch. Guardrails uses this

Give each its own long random string (openssl rand -hex 32). A trader token cannot flip the kill switch.