fix(lint): Acknowledge discarded print and close return values

errcheck flagged unchecked returns throughout the CLI's output paths
and response cleanup. Those returns are never actionable in practice:
console writes only fail on broken pipe or a full disk, and a deferred
network resource close has nothing useful to do with the error.
Discard them explicitly rather than silencing the linter, so any
genuinely unchecked error elsewhere stays visible.

Add lint to the `make qa` target so the release flow catches this
locally rather than only in CI.

Author: nfebe

Makefile

@@ -17,7 +17,7 @@ help:
 	@echo "make fmt-check     - Check gofmt formatting"
 	@echo "make vet           - Run go vet"
 	@echo "make lint          - Run golangci-lint"
-	@echo "make qa            - Run fmt-check, vet, and tests"
+	@echo "make qa            - Run fmt-check, vet, lint, and tests"
 	@echo "make clean         - Clean build artifacts"
 
 deps:
@@ -52,7 +52,7 @@ lint:
 lint-install:
 	go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@latest
 
-qa: fmt-check vet test
+qa: fmt-check vet lint test
 
 clean:
 	rm -f $(BINARY_NAME)