fix(shell): preserve pipeline verdict semantics

tools/e2e-gateway-verify-supported.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+# Exit 0 only when the capability probe itself succeeds and advertises verify.
+# A failed help command and a successful response without verify are both
+# unsupported, matching the historical e2e-install-test.sh conditional.
+set -uo pipefail
+
+gateway_help_rc=0
+gateway_help="$(mosaic gateway --help 2>&1)" || gateway_help_rc=$?
+[[ "$gateway_help_rc" -eq 0 ]] || exit 1
+grep -q 'verify' <<<"$gateway_help"

tools/e2e-install-test.sh

@@ -136,8 +136,7 @@ fi
 echo "=== [inner] Running mosaic gateway verify ==="
 # `gateway verify` was added in feat/mosaic-first-run-ux.
 # If the installed version pre-dates this, skip gracefully.
-gateway_help="$(mosaic gateway --help 2>&1 || true)"
-if ! grep -q 'verify' <<<"$gateway_help"; then
+if ! bash /repo/tools/e2e-gateway-verify-supported.sh; then
   echo "[SKIP] 'mosaic gateway verify' not available in installed version ${INSTALLED_VERSION}."
   echo "[SKIP] This command was added in the feat/mosaic-first-run-ux release."
   echo "[SKIP] Re-run after the new version is published to validate this step."