chore: publish binary release artifacts

[0xRaghu]

Summary

• replace the tag-only Homebrew bump workflow with a GoReleaser release workflow that uploads cross-platform binary archives and checksums
• keep the Homebrew tap update path through the existing GoReleaser config
• update the GoReleaser archive syntax to the current v2 format
• replace the broken external plugin repo README link with the local Claude Code plugin section anchor

Verification

• go test ./...
• ruby -e 'require "yaml"; YAML.load_file(".github/workflows/release.yml")'
• go run github.com/goreleaser/goreleaser/v2@v2.9.0 check
• go run github.com/goreleaser/goreleaser/v2@v2.9.0 release --snapshot --clean

Closes #11
Closes #12