feat(ult): implement creation-bound condition variables - #5942

On November 2, 2026, GitHub will restrict `pull_request_target` on public repositories by default. To continue allowing the event trigger, configure an Actions policy. Learn more: https://gh.io/securely-using-pull_request_target#default-policy-for-pull_request_target

Technical debt entry over 1000 characters: state the gap first (what differs from the console, what is unverified, what throws) and keep only the behaviour it needs: 1584 characters