fix(ci): make canvas docker probe pipefail-safe

.gitea/workflows/publish-canvas-image.yml

@@ -102,12 +102,14 @@ jobs:
           set -euo pipefail
           echo "::group::Docker daemon health check"
           echo "Runner: ${HOSTNAME:-unknown}"
-          docker info 2>&1 | head -5 || {
+          docker_info="$(docker info 2>&1)" || {
             echo "::error::Docker daemon is not accessible at /var/run/docker.sock"
             echo "::error::Runner: ${HOSTNAME:-unknown}"
+            printf '%s\n' "${docker_info}"
             echo "::error::Check: (1) daemon running, (2) runner user in docker group, (3) sock perms 660+"
             exit 1
           }
+          printf '%s\n' "${docker_info}" | sed -n '1,5p'
           echo "Docker daemon OK"
           echo "::endgroup::"