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/referral.go

@@ -32,18 +32,18 @@ func (s ResolutionState) String() string {
 }
 
 type Referral struct {
-	Name     string
-	Qtype    uint16
-	Qclass   uint16
+	Name      string
+	Qtype     uint16
+	Qclass    uint16
 	Bailiwick string
 
 	Addresses []net.IP
 	State     ResolutionState
 
-	NSName  string
-	Parent  *Referral
-	Depth   int
-	Prob    float64
+	NSName string
+	Parent *Referral
+	Depth  int
+	Prob   float64
 }
 
 func NewReferral(name string, qtype uint16, bailiwick string, depth int, prob float64, parent *Referral) *Referral {
@@ -81,7 +81,7 @@ func (r *Referral) SetAddresses(addrs []net.IP) {
 }
 
 type CircularReferralError struct {
-	Name string
+	Name  string
 	Chain []string
 }
 
@@ -90,7 +90,7 @@ func (e *CircularReferralError) Error() string {
 }
 
 type UnresolvableNameserverError struct {
-	Name string
+	Name   string
 	Reason string
 }