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/output/runner.go

@@ -0,0 +1,36 @@
+package output
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/hits/ExploreDNS/internal/traverse"
+)
+
+func RunTraversal(ctx context.Context, traverser *traverse.Traverser, cfg *Config, formatter Formatter, domain string) ([]traverse.TraversalResult, error) {
+	if traverser == nil {
+		return nil, fmt.Errorf("traverser is required")
+	}
+	if cfg == nil {
+		cfg = DefaultConfig()
+	}
+	if formatter == nil {
+		formatter = NewFormatter(cfg, nil)
+	}
+
+	traverser.SetHooks(AttachHooks(cfg, formatter))
+
+	results, err := traverser.Traverse(ctx, domain)
+	if err != nil {
+		return results, err
+	}
+
+	if err := formatter.WriteSummary(results); err != nil {
+		return results, err
+	}
+	if err := formatter.Flush(); err != nil {
+		return results, err
+	}
+
+	return results, nil
+}