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/hooks.go

@@ -0,0 +1,31 @@
+package traverse
+
+type EventStage int
+
+const (
+	EventStart EventStage = iota
+	EventComplete
+)
+
+type TraversalEvent struct {
+	Stage     EventStage
+	Result    TraversalResult
+	IsResolve bool
+}
+
+type EventHandler func(TraversalEvent)
+
+type TraverserHooks struct {
+	OnEvent EventHandler
+}
+
+func (h *TraverserHooks) emit(stage EventStage, result TraversalResult, isResolve bool) {
+	if h == nil || h.OnEvent == nil {
+		return
+	}
+	h.OnEvent(TraversalEvent{
+		Stage:     stage,
+		Result:    result,
+		IsResolve: isResolve,
+	})
+}