chore: remove outdated plan documents

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

fix: upgrade GoReleaser to v2 for config compatibility

- Use goreleaser-action@v6 with version ~> v2
- Add HOMEBREW_TAP_TOKEN to release workflow

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>