style(sdk): SDK默认列表MD3容器化 — meow_listview_create默认container=1(行=surfaceContainer圆角卡+空隙+去分隔线+卡内tonal选中)，hello/files/ncm/reader等用默认renderer的App开箱即MD3(用户2026-09-04反馈默认仍扁平)；需平坦宿主可set_container(0)回退(宿主测试test_meow_ui_widgets/listvirt补set_container(0)锁扁平基线)。0warning，宿主测试全过(widgets ALL PASS/md3 PASS/swipe 35-0/listvirt 44-0)。meow_ui.a变需重编+重链四App

patch_v2/sdk/test_meow_ui_widgets.c

@@ -318,6 +318,7 @@ int main(void)
      * lv 位于 (20,240,320,112)item_h=56 → 行0 y240..296、行1 296..352。
      * 断言全部「画完读 back_buf 像素」（region_has/px_near），非目检。 */
     meow_widget *lv = W(meow_listview_create(20, 240, 320, 112, 4, lv_src, NULL, MEOW_LIST_SEL_SINGLE));
+    meow_listview_set_container(lv, 0);   /* 锁扁平基线：SDK 默认已变 MD3 容器，此测试专测 set_container(0) 扁平回退路径 */
     assert(meow_listview_set_item_h(lv, 56) == 56);
     const meow_theme *lth = meow_theme_get();
     int lvx = 20, lvy = 240, lvw = 320, lvh = 112, itemh = 56;