fix(release): publish manifest without plugin build artifacts

[rozsazoltan]

Summary

Fixes the release/publish workflows so mise-php releases do not build or upload a custom plugin archive.

Fixed

• Remove the custom plugin zip build from the release workflow.
• Remove Lua, luarocks, and dkjson from manifest generation.
• Generate manifest.json with Python only.
• Point manifest downloadUrl to the GitHub tag archive used by mise plugin installs.
• Keep the tag-based publish workflow manifest-only.

Context

mise installs the plugin from repository tags, so publishing a separate plugin archive is unnecessary. The previous workflow also failed because dkjson was not available in the GitHub Actions Lua environment.

Testing

• Parsed GitHub Actions workflow YAML.
• Ran git diff checks.
• Smoke-tested manifest generation and verified the tag archive downloadUrl.