feat(cli): always print version header first, add --no-version flag

Previously the version banner only printed via PersistentPreRun, which
Cobra skips for --help and bare invocations. It now prints from main()
before Cobra parses anything, so it's the first line for every command.
Suppressible with --no-version; skipped for the version subcommand to
avoid duplicating its own output.

cmd/relspec/main.go

@@ -6,6 +6,7 @@ import (
 )
 
 func main() {
+	printVersionHeader(os.Args[1:])
 	if err := rootCmd.Execute(); err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)