maglevt: show FQDN in header instead of config paths; v1.0.1

Replace the cfgPath field in the TUI header with the system's
fully-qualified hostname via gethostname + CNAME lookup, matching
what `hostname -f` produces.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cmd/tester/view.go

@@ -149,7 +149,7 @@ func (m Model) viewHeader() string {
 	}
 	line := fmt.Sprintf(
 		"maglevt — %s — interval: %s  timeout: %s  header: %s  [%s]  uptime: %s",
-		m.cfgPath,
+		m.host,
 		m.opts.Interval,
 		m.opts.Timeout,
 		m.opts.Header,