Cattery continue to restart jobs event on closed PR's

[AndWeHaveAPlan]

seems to be retriggering failed CI runs even 9 more times after a PR is merged so it eats up CI resources for us needlessly and makes github runners unavailable

https://matrix.to/#/!JUeaZUiYbdrvzvtwSL:parity.io/$yplLTZj_uy2rALfBqLzuptinrFsi_rK_uXJ2luLG3rM?via=parity.io

Example with 9 attempts: https://github.com/paritytech/foundry-polkadot/actions/runs/19671811728

[alvicsam]

2 bugs to solve:

1. Job restarter works even in closed PRs
2. Agent sends server command to restart on non-preemption event (SIGTERM)