test(client): KPI 卡三主题 golden（design-distill 阶段4 Flutter 侧首个还原闸）

test/theme/kpi_card_golden_test.dart：4 张 KPI 卡 × A/B/C 三主题 golden，
产出 goldens/kpi_strip_{a,b,c}.png。验证 KpiCard 还原原型 .kpi 结构/色调
（icon 芯片 info/blue/warn/alert 分档着色、alert 值取 accent、软底随主题换）。
更新基准：flutter test --update-goldens test/theme/kpi_card_golden_test.dart

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TSKEiHsvauyxYUW2itzUXX

client/test/theme/kpi_card_golden_test.dart

@@ -0,0 +1,79 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:jiu_client/core/theme/themes.dart';
+import 'package:jiu_client/core/theme/app_tokens.g.dart';
+import 'package:jiu_client/widgets/kpi_card.dart';
+
+/// design-distill 阶段4（Flutter 侧）：KPI 卡组件 golden。
+/// 渲染库存列表的 4 张 KPI 卡 × 三主题，产出 png 供与原型 `.kpi` 并排目检。
+/// 更新基准：flutter test --update-goldens test/theme/kpi_card_golden_test.dart
+void main() {
+  const cardW = 300.0;
+  Widget strip() => Padding(
+        padding: const EdgeInsets.all(12),
+        child: Row(
+          mainAxisSize: MainAxisSize.min,
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: const [
+            SizedBox(
+                width: cardW,
+                child: KpiCard(
+                    title: '商品总数',
+                    value: '1284',
+                    icon: Icons.inventory_2,
+                    tone: KpiTone.info,
+                    delta: '种 · 点击清筛选')),
+            SizedBox(width: 12),
+            SizedBox(
+                width: cardW,
+                child: KpiCard(
+                    title: '在库数量',
+                    value: '18920',
+                    icon: Icons.warehouse_outlined,
+                    tone: KpiTone.blue,
+                    delta: '件')),
+            SizedBox(width: 12),
+            SizedBox(
+                width: cardW,
+                child: KpiCard(
+                    title: '库存预警',
+                    value: '17',
+                    icon: Icons.warning_amber,
+                    tone: KpiTone.warn,
+                    delta: '需补货')),
+            SizedBox(width: 12),
+            SizedBox(
+                width: cardW,
+                child: KpiCard(
+                    title: '缺货商品',
+                    value: '6',
+                    icon: Icons.remove_shopping_cart,
+                    tone: KpiTone.alert)),
+          ],
+        ),
+      );
+
+  for (final theme in ['a', 'b', 'c']) {
+    testWidgets('KPI strip golden · theme $theme', (tester) async {
+      tester.view.physicalSize = const Size(2560, 380);
+      tester.view.devicePixelRatio = 2.0;
+      addTearDown(tester.view.resetPhysicalSize);
+      addTearDown(tester.view.resetDevicePixelRatio);
+
+      await tester.pumpWidget(MaterialApp(
+        debugShowCheckedModeBanner: false,
+        theme: buildTheme(theme),
+        home: Scaffold(
+          backgroundColor: appTokensOf(theme).bg,
+          body: Align(alignment: Alignment.topCenter, child: strip()),
+        ),
+      ));
+      await tester.pumpAndSettle();
+
+      await expectLater(
+        find.byType(MaterialApp),
+        matchesGoldenFile('goldens/kpi_strip_$theme.png'),
+      );
+    });
+  }
+}