Adopt GoReleaser release packaging

[itamaker]

Summary

• replace the manual tarball release flow with GoReleaser
• add publishing docs and a Homebrew cask render script
• update CI and release workflows to validate and publish via GoReleaser

Verification

• go test ./...
• go build ./cmd/go-chrome-ai
• goreleaser check
• goreleaser release --snapshot --clean --skip=publish
• render-homebrew-cask.sh output matches the current v1.0.2 cask structure