fix: avoid kill timeout exit delays

[rajanpanth]

Summary

• release the kill-timeout timer's event-loop reference
• add regression coverage for cooperative processes that stop before force-kill is needed

Problem

When killTimeout is enabled, KillOthers schedules a referenced timer before sending the initial termination signal. If all targeted processes stop cooperatively, that timer is the only remaining active handle and keeps concurrently running until the full timeout expires.

Fix

Unreference the force-kill timer. A child process that is still running continues to keep Node alive, so the timer can still deliver SIGKILL; once every child has stopped, the timer no longer delays exit.

Testing

• pnpm exec vitest run --project unit lib/flow-control/kill-others.spec.ts
• pnpm test
• pnpm exec vitest --coverage
• pnpm typecheck
• pnpm lint
• pnpm exec prettier --check "**/*.{json,y?(a)ml,md}"
• pnpm build
• pnpm test:smoke

[coveralls]

coverage: 98.858%. remained the same — rajanpanth:fix/kill-timeout-exit-delay into open-cli-tools:main

[gustavohenke]

Nice find!