fix(cmd): handle errors and improve output formatting

* update error handling in various commands to use blank identifier
* enhance output formatting for better readability
* add golangci-lint to Makefile for linting checks

Makefile

@@ -20,9 +20,10 @@ vet:
 fmt:
 	go fmt ./...
 
-## lint: vet + format check
+## lint: vet + format check + golangci-lint
 lint: vet
 	test -z "$$(gofmt -l .)" || (echo "gofmt needed:"; gofmt -l .; exit 1)
+	golangci-lint run ./...
 
 ## clean: remove build artifacts
 clean: