fix(infra): drop consumer-less gateway supervision exports

333c4f9a61 and 244f4965dc landed six exports with no production
consumers, failing the hard-zero deadcode gate on every PR: a dead
re-export block in restart-handoff (the contract module's real importer
uses it directly), three result/mode types only referenced inside their
own modules, and two supervision symbols whose only consumers were their
tests. The types and helpers stay defined for the in-flight supervisor
work to re-export alongside real consumers; the supervision test now
proves mode resolution through the public isGatewayExternallySupervised
surface.

src/cli/daemon-cli/restart-lock-replacement.ts

@@ -5,7 +5,7 @@ import {
 } from "../../infra/gateway-lock.js";
 import { sleep } from "../../utils.js";
 
-export type GatewayLockReplacementWaitResult =
+type GatewayLockReplacementWaitResult =
   | { status: "replacement"; attemptsUsed: number }
   | { status: "timeout" };