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/main.go

@@ -108,7 +108,7 @@ func run() error {
 	}
 
 	m := Model{
-		cfgPath: strings.Join(cfgPaths, ", "),
+		host:    fqdn(),
 		vips:    vips,
 		opts:    opts,
 		startAt: time.Now(),
@@ -158,6 +158,24 @@ func run() error {
 // deterministic TUI layout: within a file, frontends are visited
 // in name-sorted order; across files, the first occurrence of each
 // tuple wins and fixes its slot in the output.
+// fqdn returns the system's fully-qualified hostname: gethostname(2)
+// via os.Hostname() for the short name, then a CNAME lookup to reach
+// the canonical form the resolver would hand back — the same two-step
+// dance `hostname -f` performs. Falls back to the short name when the
+// resolver has nothing to add, so the TUI header always renders.
+func fqdn() string {
+	h, err := os.Hostname()
+	if err != nil {
+		return "unknown"
+	}
+	if cname, err := net.LookupCNAME(h); err == nil {
+		if s := strings.TrimSuffix(cname, "."); s != "" {
+			return s
+		}
+	}
+	return h
+}
+
 func buildVIPsUnion(cfgs []*config.Config, cfgPaths []string, filterRe *regexp.Regexp, opts probeOpts) []*vipState {
 	_ = cfgPaths // reserved for future diagnostics (e.g. which file this tuple came from)
 	type key struct {