fix: address code review issues on PR #9

- gofmt main.go to fix tab indentation in main() body
- stats.go ComputeSummary: return nil when Answers and ByType are empty
- dns/types.go: remove duplicate ParseQueryType (dead code)
- formatter.go: log hook errors to stderr when Debug > 0; add Debug to Config
- text.go referralID: remove redundant depth==0 branch
- text.go writeServers: remove version lookup placeholder string

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: multica-agent <github@multica.ai>

internal/traverse/stack.go

@@ -3,7 +3,7 @@ package traverse
 const DefaultMaxDepth = 20
 
 type Stack struct {
-	items   []*Referral
+	items    []*Referral
 	maxDepth int
 }
 
@@ -12,7 +12,7 @@ func NewStack(maxDepth int) *Stack {
 		maxDepth = DefaultMaxDepth
 	}
 	return &Stack{
-		items:   make([]*Referral, 0),
+		items:    make([]*Referral, 0),
 		maxDepth: maxDepth,
 	}
 }