Fix EXPLAIN children count when both options and SETTINGS present

Count EXPLAIN-level options and statement-level SETTINGS separately
when both are present.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kyleconroy

internal/explain/statements.go

@@ -908,7 +908,10 @@ func explainExplainQuery(sb *strings.Builder, n *ast.ExplainQuery, indent string
 	if format != nil {
 		children++
 	}
-	if n.HasSettings || hasSettingsAfterFormat {
+	if n.HasSettings {
+		children++
+	}
+	if hasSettingsAfterFormat {
 		children++
 	}
 

parser/testdata/02704_storage_merge_explain_graph_crash/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt12": true
-  }
-}
+{}