fix: output preamble in generated file

cmd/tea/gen_id.go

@@ -16,8 +16,11 @@ import (
 	"github.com/spf13/cobra"
 )
 
-var (
+const (
 	outputPreamble = "// Code generated by tea. DO NOT EDIT.\n\n"
+)
+
+var (
 	// genIDCmd represents the id command
 	genIDCmd = &cobra.Command{
 		Use:   "id",
@@ -135,10 +138,6 @@ func (i IDs) generate() ([]byte, error) {
 	var genData []byte
 	var err error
 
-	if _, err = output.WriteString(outputPreamble); err != nil {
-		return nil, fmt.Errorf("writing output preamble: %w", err)
-	}
-
 	for typ := range i {
 		//nolint:gocritic,exhaustive
 		switch typ {
@@ -361,6 +360,9 @@ func runGenerateIDs(sourceFilePath, outputFilePath string) error {
 		}
 	}()
 
+	if _, err = outputFile.Write([]byte(outputPreamble)); err != nil {
+		return cmderrors.NewCommandError(fmt.Errorf("writing output preamble: %w", err), cmderrors.CodeIO)
+	}
 	if _, err = outputFile.Write(ids.generateHeader()); err != nil {
 		return cmderrors.NewCommandError(fmt.Errorf("writing output header: %w", err), cmderrors.CodeIO)
 	}