security-gate.sh checked only `command -v node` before running
`npm test -w frontend`. In the CI security-gate job, node is in PATH
(from actions/setup-node) but root node_modules are NOT installed
(npm ci was removed to prevent OOM). This caused the frontend test to
fail with "Cannot find module vitest".
Fix: also require node_modules/.bin/vitest to exist. Without it the
step SKIPs gracefully — frontend tests are already covered by the
dedicated frontend-tests CI job which runs first.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
