feat: port to V2 plugin API with plugin-compat layer - #79

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-node@v4, actions/upload-artifact@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Tarball version (opencode-supabase-0.5.1.tgz) is the changesets-managed package.json version — contents are built from this checkout. Run identity is the SHA-256 below.