feat: implement output formatting and display (HAN-383)

Add text and JSON formatters with real-time progress via traverser hooks,
summary statistics, and CLI integration for --show-* and --json flags.

Co-authored-by: multica-agent <github@multica.ai>

internal/traverse/traverser.go

@@ -16,6 +16,7 @@ type TraverserConfig struct {
 	RootConfig  *dns.RootDiscoveryConfig
 	QueryConfig *dns.QueryConfig
 	RootAddrs   []net.IP
+	Hooks       *TraverserHooks
 }
 
 func DefaultTraverserConfig() *TraverserConfig {
@@ -57,6 +58,13 @@ func (t *Traverser) SetExchange(fn dns.ExchangeFunc) {
 	t.exchange = fn
 }
 
+func (t *Traverser) SetHooks(hooks *TraverserHooks) {
+	if t.config == nil {
+		t.config = DefaultTraverserConfig()
+	}
+	t.config.Hooks = hooks
+}
+
 func (t *Traverser) Traverse(ctx context.Context, name string) ([]TraversalResult, error) {
 	name = miekgdns.Fqdn(name)
 
@@ -94,9 +102,19 @@ func (t *Traverser) Traverse(ctx context.Context, name string) ([]TraversalResul
 			cache = rootCache.Child()
 		}
 
+		if t.config.Hooks != nil {
+			t.config.Hooks.emit(EventStart, TraversalResult{Referral: ref}, false)
+		}
+
 		resp := t.processReferral(ctx, ref, cache)
+
+		result := TraversalResult{Referral: ref, Response: resp}
+		if t.config.Hooks != nil {
+			t.config.Hooks.emit(EventComplete, result, false)
+		}
+
 		mu.Lock()
-		results = append(results, TraversalResult{Referral: ref, Response: resp})
+		results = append(results, result)
 		mu.Unlock()
 
 		if resp.IsTerminal() {
@@ -266,8 +284,16 @@ func (t *Traverser) ResolveNS(ctx context.Context, nsName string, cache *InfoCac
 			cacheForStep = traversalCache.Child()
 		}
 
+		if t.config.Hooks != nil {
+			t.config.Hooks.emit(EventStart, TraversalResult{Referral: current}, true)
+		}
+
 		resp := t.processReferral(ctx, current, cacheForStep)
 
+		if t.config.Hooks != nil {
+			t.config.Hooks.emit(EventComplete, TraversalResult{Referral: current, Response: resp}, true)
+		}
+
 		if resp.Type == RespAnswer && len(resp.Decoded.Answers) > 0 {
 			for _, rr := range resp.Decoded.Answers {
 				if a, ok := rr.(*miekgdns.A); ok {