fix: publish JavaScript plugin entrypoint

[tsukinoko-kun]

Summary

OpenCode GUI uses a Node plugin host, while OpenCode CLI uses Bun.

The package exposed index.ts directly. Node refuses TypeScript stripping for files inside node_modules, causing:

ERR_UNSUPPORTED_NODE_MODULES_TYPE_STRIPPING

This prevented the GUI from loading the plugin. CLI continued working because Bun supports TypeScript package entrypoints.

Fix

• Compile index.ts to dist/index.js
• Publish the JavaScript entrypoint only
• Build automatically during npm pack/publish
• Add a Node package-import smoke test to the publish workflow
• Bump version to 0.2.3

Verified with OpenCode GUI, package build, npm tarball, and bare Node package import.

Why my earlier attempt failed

I created a bad testing environment that worked around this issue. It was not a new OpenCode GUI update but my bad testing setup. My new testing setup is much closer to how OpenCode GUI actually loads the plugin from npm.

Sorry for the earlier mistake. My earlier attempt was still right but not fully there.

Closes #7

[tsukinoko-kun]

I can't test the CI change. Please double check yourself before merging.

[IgnisDa]

Thanks for this!