Only publish specific versions to ghcr.io

Author: Patrick J. McNerthney

.github/workflows/ci.yaml

@@ -217,6 +217,8 @@ jobs:
   # pushes them as a multi-platform package. We only push the package it the
   # XPKG_ACCESS_ID and XPKG_TOKEN secrets were provided.
   push-xpkg:
+    # Don't publish unless we were run with an explicit version.
+    if: ${{ inputs.version != '' }}
     needs:
       - build-xpkg
     runs-on: ubuntu-24.04