* update error handling in various commands to use blank identifier
* enhance output formatting for better readability
* add golangci-lint to Makefile for linting checks
Advertise DocumentRangeFormattingProvider in server capabilities and
implement rangeFormat: formats the complete document, then returns an
edit covering only the minimal changed-line region that overlaps the
client's selection. Also includes gofmt alignment fixes across lint
and format packages.