The publisher read the PR number from the CI run's pull_requests
payload. GitHub keeps that payload empty for fork runs, so the job
printed 'No pull request is associated' and stopped on every fork PR.
Resolve the PR from the run's head owner, branch, and SHA instead.
The SHA match skips runs that a newer push superseded.
A fork PR also has no CI review comment, because the live poller
skips forks. The publisher now logs this and exits clean instead of
raising; the evidence stays in the workflow artifact.
