* ci: host plugin tarballs as release assets, drop marketplace seed
Attach each published sandboxed plugin's bundle to the GitHub release
changesets creates, giving the decentralized registry (RFC 0001) a
stable public URL per version. Remove the legacy marketplace seed
workflow, which has been failing since the post-#1057 plugin layout
broke its bundler and is superseded by the registry.
* ci: harden plugin tarball attach script
Address review feedback: guard per-directory package.json parsing so one
bad manifest doesn't abort the step, treat an empty PUBLISHED_PACKAGES
output as no-op, and fail fast when GITHUB_REPOSITORY is missing. Note
the publish-only path limitation in the workflow.
Matt Kane
bb9bc26f6c