fix(acp): run exit cleanup when stdin closes

[codefromthecrypt]

Summary

ACP mode does not receive SIGTERM/SIGINT signals like interactive mode, the best signal is STDIN being closed. Run exit cleanup on that to flush telemetry.

Tested with: npm run test:integration:sandbox:none -- --testNamePattern="should flush telemetry"

Pre-Merge Checklist

• [ ] Updated relevant documentation and README (if needed)
• [x] Added/updated tests (if needed)
• [ ] Noted breaking changes (if any)
• [ ] Validated on required platforms/methods:
  • [ ] MacOS
    • [x] npm run
    • [ ] npx
    • [ ] Docker
    • [ ] Podman
    • [ ] Seatbelt
  • [ ] Windows
    • [ ] npm run
    • [ ] npx
    • [ ] Docker
  • [ ] Linux
    • [ ] npm run
    • [ ] npx
    • [ ] Docker