ci: read the org-scoped ZEGIT_CI_PACKAGE_TOKEN, not a repo-local name

The publish path failed at registry login on every dispatch (runs 18,
20) because it read `secrets.ZEGIT_PACKAGE_TOKEN`, a name that exists
nowhere. The package-write token every zegit-zoo image workflow uses is
ZEGIT_CI_PACKAGE_TOKEN, held above repository scope, so this repository
can read it under that name — no second token, no second copy to rotate.

.github/workflows/build-image-gitea.yml

@@ -90,11 +90,11 @@ jobs:
       - name: Registry login
         if: ${{ steps.meta.outputs.push == 'true' }}
         env:
-          TOKEN: ${{ secrets.ZEGIT_PACKAGE_TOKEN }}
+          TOKEN: ${{ secrets.ZEGIT_CI_PACKAGE_TOKEN }}
         run: |
           set -euo pipefail
           if [ -z "${TOKEN:-}" ]; then
-            echo "::error::ZEGIT_PACKAGE_TOKEN is not set, so this dispatch would build an image and push nothing. Issue a package-write token and store it as this secret."
+            echo "::error::ZEGIT_CI_PACKAGE_TOKEN is not visible to this run. It is the org-scoped package-write token every zegit-zoo image workflow uses (docs: flux-config docs/rotation/forge-secrets.yaml); this repository must be able to read the org secret, and the name must match."
             exit 1
           fi
           mkdir -p "$HOME/.docker"