publish-bundle.yml: emit the pinned component versions into the release body

[dfattal]

Every bundle release body (v2.3.4 → v2.3.7) is only the auto-generated Full Changelog line; the pins live in versions.json and are invisible to a user reading the release page. The release step should render versions.json into a table in the body (runtime, plug-in, shell, MCP, demos, opt-in browser) plus the compare link. v2.3.7's body was backfilled by hand as the template.

🤖 Generated with Claude Code

https://claude.ai/code/session_01MZS571NBBnZ2n9d8CXtJwz