chore: improve generator-jhipster maintenance path

[quyentonndbs]

Summary:

• Add or tighten focused edge-case tests or type assertions in cli/index.ts, test/api.spec.ts related to TypeScript, frontend tooling, test stability, build fixes; avoid docs-only changes and broad refactors.
• Keep the change narrow so it is straightforward to review.

Notes:

• I kept this scoped to the relevant implementation and tests.