Print banner to stdout and include signature in machine welcome message

Address Copilot review: use stdout for banner to match other interactive
output, and include the signature in machine output welcome_message for
consistency with interactive output.

Author: robzolkos

internal/commands/banner.go

@@ -22,14 +22,14 @@ const banner = `
 ⠀⢁⠈⢀⠠⠐⠀⡈⠠⠀⡀⠄⠠⠐⠀⠂⠁⠐⠀⠂⡈⢀⠁⠐⡀⠄⠠⠀⠄⢀⠐⠀⠂⠐⠀⠂⡀⢁⠈⡀⠄⠠⠀⠐⢀⠈⡀⢁⠐⢀⠐⠀⡁⢈⠀⡁⠀⠄⠐⠀⠂⠁⡈⢀⠁⡈⢀⠁⡈⢀⠀⡀⠄⠂⠁⠀⠄⠠⠈⠀
 `
 
-// printBanner prints the Fizzy braille art banner to stderr.
+// printBanner prints the Fizzy braille art banner to stdout.
 // Only prints in interactive TTY mode, never in machine/piped output.
 func printBanner() {
 	if IsMachineOutput() {
 		return
 	}
-	if !isatty.IsTerminal(os.Stderr.Fd()) && !isatty.IsCygwinTerminal(os.Stderr.Fd()) {
+	if !isatty.IsTerminal(os.Stdout.Fd()) && !isatty.IsCygwinTerminal(os.Stdout.Fd()) {
 		return
 	}
-	fmt.Fprint(os.Stderr, banner)
+	fmt.Print(banner)
 }

internal/commands/signup.go

@@ -527,7 +527,7 @@ func runSignupComplete(cmd *cobra.Command, args []string) error {
 	summary := "Configuration saved."
 
 	if name != "" {
-		result["welcome_message"] = welcomeMessage + "\n" + welcomeSignoff
+		result["welcome_message"] = welcomeMessage + welcomeSignature + welcomeSignoff
 		result["is_new_user"] = true
 	}