chore(backlog): 记录 g138 完成

.ua/backlog.json

@@ -1467,7 +1467,7 @@
       "motivation": "筛选条件几乎都要「起止日期」，datePicker 只有单日：调用方只能并排放两个选择器，用户看不出选了什么区间，也拿不到排序保证",
       "acceptance": "datePicker 新增 range/end/onRangeChange：首点定起点不收弹层、次点定终点并排序，区间内部有底色；文档 props/steps 与演示同步；npm run check 全绿",
       "notes": "自补：既有组件可用性细节",
-      "status": "open"
+      "status": "done"
     }
   ]
 }

.ua/iterations.log

@@ -182,3 +182,4 @@
 {"ts":"2026-10-26T15:27:19+08:00","id":"g135","result":"done","commit":"21950d9","summary":"form 新增 columns（1/2/3）复用 grid 铺列，窄屏自动单列、按钮区整行；demo 注册表单改两列"}
 {"ts":"2026-10-26T15:28:20+08:00","id":"g136","result":"done","commit":"f6706c1","summary":"新增 link（站外自动补 ↗ 与 rel=noopener noreferrer 并播报新窗口，muted/disabled 齐全），组件 65→66；sync-counts 首跑改写 3 份文档计数"}
 {"ts":"2026-10-26T15:29:51+08:00","id":"g137","result":"done","commit":"55da08f","summary":"演示页头部加暗色主题开关（data-theme + localStorage 记忆，初值跟随系统），--page-* 变量改为响应显式主题、媒体查询仅兜未指定时"}
+{"ts":"2026-10-26T15:31:27+08:00","id":"g138","result":"done","commit":"1af4e57","summary":"datePicker 新增 range/end/onRangeChange：首点定起点不收弹层、次点定终点并自动排序，区间内部低比重底色连成一条"}