Bash cutover verification scripts exited early under set -e despite successful checks

A Node/TypeScript gateway cutover harness had passing health checks but its Bash cutover and post-cutover verification scripts exited early or misreported failure. The scripts used set -euo pipefail, post-increment arithmetic such as ((elapsed++)) / ((PASS_COUNT++)), brittle command-output parsing for npm preflight status, and exact JSON-shape assumptions for RPC verification.