refactor(cli): modularize CLI — extract parser, runner, report and main logic into dedicated files

benchmark_cherrypick/lib/cli/report/csv_report.dart

@@ -0,0 +1,21 @@
+import 'report_generator.dart';
+
+class CsvReport extends ReportGenerator {
+  @override
+  final List<String> keys = [
+    'benchmark','chainCount','nestingDepth','mean_us','median_us','stddev_us',
+    'min_us','max_us','trials','timings_us','memory_diff_kb','delta_peak_kb','peak_rss_kb'
+  ];
+  @override
+  String render(List<Map<String, dynamic>> rows) {
+    final header = keys.join(',');
+    final lines = rows.map((r) =>
+      keys.map((k) {
+        final v = r[k];
+        if (v is List) return '"${v.join(';')}"';
+        return (v ?? '').toString();
+      }).join(',')
+    ).toList();
+    return ([header] + lines).join('\n');
+  }
+}

benchmark_cherrypick/lib/cli/report/json_report.dart

@@ -0,0 +1,10 @@
+import 'report_generator.dart';
+
+class JsonReport extends ReportGenerator {
+  @override
+  List<String> get keys => [];
+  @override
+  String render(List<Map<String, dynamic>> rows) {
+    return '[\n${rows.map((r) => '  $r').join(',\n')}\n]';
+  }
+}

benchmark_cherrypick/lib/cli/report/pretty_report.dart

@@ -0,0 +1,15 @@
+import 'report_generator.dart';
+
+class PrettyReport extends ReportGenerator {
+  @override
+  final List<String> keys = [
+    'benchmark','chainCount','nestingDepth','mean_us','median_us','stddev_us',
+    'min_us','max_us','trials','memory_diff_kb','delta_peak_kb','peak_rss_kb'
+  ];
+  @override
+  String render(List<Map<String, dynamic>> rows) {
+    final header = keys.join('\t');
+    final lines = rows.map((r) => keys.map((k) => (r[k] ?? '').toString()).join('\t')).toList();
+    return ([header] + lines).join('\n');
+  }
+}

benchmark_cherrypick/lib/cli/report/report_generator.dart

@@ -0,0 +1,4 @@
+abstract class ReportGenerator {
+  String render(List<Map<String, dynamic>> results);
+  List<String> get keys;
+}