fix(ci): restore preflight image cleanup marker and remove obsolete publish-container tests

- Restore build_attempted=1 in ci-preflight.sh so the exit trap
  removes the temporary image tag
- Remove publish-container.test.ts and its harness (publication
  workflow and script were removed in fff284aa)
- Update deploy-workflow-contract and docker-build-contract tests
  to assert that publication has been removed

scripts/ci-preflight.sh

@@ -38,6 +38,7 @@ pnpm install --frozen-lockfile
 pnpm exec playwright install chromium
 export NEWS_E2E_IMAGE="$image"
 export NEWS_E2E_RELEASE="$sha"
+build_attempted=1
 DOCKER_BUILDKIT=1 docker build --network=host --progress=plain \
   --build-arg NEXT_DEPLOYMENT_ID="$sha" -t "$image" .
 NEWS_E2E_IMAGE="$image" NEWS_E2E_RELEASE="$sha" node --import tsx e2e/news-real/run.ts