tdt-loss: add TDT loss kernel - #882

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

HF router HTTP 403: {"error":"This authentication method does not have sufficient permissions to call Inference Providers on behalf of user kernels-bot"}