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/cache.go

@@ -9,10 +9,10 @@ import (
 )
 
 type InfoCache struct {
-	parent   *InfoCache
-	mu       sync.RWMutex
-	ns       map[string][]string
-	glue     map[string][]net.IP
+	parent *InfoCache
+	mu     sync.RWMutex
+	ns     map[string][]string
+	glue   map[string][]net.IP
 }
 
 func NewInfoCache(parent *InfoCache) *InfoCache {