feat(ds-flow): Phase 4.1 — 清 adaptive_menu 唯一裸 Material 色

adaptive_menu.dart shadowColor: Colors.black26(冷黑)→ PangolinColors.sand950
withValues(0.24)(暖近黑,对齐 §5 暖阴影铁律)。UI 层(widgets/screens/shell)
自此零裸 Material 色。flutter analyze 通过。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/lib/widgets/adaptive_menu.dart

@@ -167,7 +167,7 @@ class _MenuCard extends StatelessWidget {
       child: Material(
         color: c.surface,
         elevation: 6,
-        shadowColor: Colors.black26,
+        shadowColor: PangolinColors.sand950.withValues(alpha: 0.24), // 暖近黑阴影(§5;非冷黑 Colors.black26)
         clipBehavior: Clip.antiAlias,
         shape: RoundedRectangleBorder(
           borderRadius: BorderRadius.circular(PangolinRadius.md),

docs/superpowers/plans/2026-07-07-frontend-ds-refactor.md

@@ -88,7 +88,7 @@
 
 Flutter 已很干净（UI 层零裸 hex），只需收尾。
 
-- [ ] 4.1 清 `client/lib/widgets/adaptive_menu.dart` 唯 1 处裸 Material 色 → 走 token
+- [x] 4.1 清 `client/lib/widgets/adaptive_menu.dart` 唯 1 处裸 Material 色 → 走 token
 - [ ] 4.2 测试字体补 CJK 子集：用 `tools/fonts/make-cjk-subset.sh` 生成 Noto Sans SC 子集放
   `client/test/fonts/`，`flutter_test_config.dart` 注册——消除 golden 中文与生产渲染差异
 - [ ] 4.3 处理现存 6 张 `client/test/golden/failures/` diff：逐张确认「原型对得上」后 `--update-goldens` 重录入库