fix(client): use andybalholm for Brotli decoding

[ryanfowler]

Summary

• replace the Google Brotli decoder with github.com/andybalholm/brotli
• update Brotli response-body wrapping and module checksums
• keep Brotli decoding coverage and fixtures current

Validation

• go test ./...
• go mod verify
• go build .
• staticcheck ./...