model attribution is recorded at the pull request as well

Trailers alone are invisible where attribution matters — a reviewer reads the pull-request body, not each commit — and a squash merge composes its message from that body, so a trailer-only record can vanish from main entirely. The template now carries a Model attribution section and CI checks it is present and non-empty. Like the DCO gate, it checks that an assertion was made, not that it is true. unrecorded is a correct answer; a guess is not.