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/output/json.go

@@ -54,8 +54,8 @@ type jsonSummary struct {
 }
 
 type jsonAnswerStat struct {
-	RData       string  `json:"rdata"`
-	Probability float64 `json:"probability"`
+	RData       string   `json:"rdata"`
+	Probability float64  `json:"probability"`
 	Records     []string `json:"records,omitempty"`
 }