test: reproduce and block unsafe broker auto-link

scripts/verify-first-broker-login.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env sh
+set -eu
+
+if [ ! -f .env ]; then
+  echo "missing .env" >&2
+  exit 1
+fi
+
+set -a
+. ./.env
+set +a
+
+restore_secure_flow() {
+  ./scripts/set-first-broker-login-mode.sh secure >/dev/null 2>&1 || true
+}
+trap restore_secure_flow 0 1 2 15
+
+npm --prefix google-e2e ci
+
+./scripts/set-first-broker-login-mode.sh vulnerable
+FIRST_BROKER_EXPECTATION=vulnerable \
+  npm --prefix google-e2e run test:first-broker
+
+./scripts/set-first-broker-login-mode.sh secure
+FIRST_BROKER_EXPECTATION=secure \
+  npm --prefix google-e2e run test:first-broker
+
+trap - 0 1 2 15
+echo "First Broker Login verified: unsafe AutoLink reproduced, Confirm Link restored"