test: add workbench layout smoke

docs/reference/cloud-workbench.md

@@ -97,10 +97,40 @@ when identity drift blocks the full journey. It never sends `POST
 must not be used as a DEV-LIVE reply, Secret, mutation, or M3/M4/M5 acceptance
 claim.
 
+## Layout Smoke
+
+`scripts/dev-cloud-workbench-layout-smoke.mjs` 是 #273 前端布局/遮挡护栏的
+runner 入口。它使用 Playwright 覆盖 `1366x768`、`1024x768` 和 `390x844`
+三档视口，检查 M3 控制区、Code Agent 输入区、右侧硬件/可信记录容器、当前
+`/gate` 内部页、外层滚动锁和内部面板滚动。命中测试使用真实 Playwright
+点击与 `document.elementsFromPoint()`；不得使用 `force: true` 或纯 DOM
+dispatch 绕过用户命中。
+
+常用命令：
+
+```sh
+node scripts/dev-cloud-workbench-layout-smoke.mjs --static --report reports/dev-gate/dev-cloud-workbench-layout.json
+node scripts/dev-cloud-workbench-layout-smoke.mjs --build --report reports/dev-gate/dev-cloud-workbench-layout-build.json
+node scripts/dev-cloud-workbench-layout-smoke.mjs --live --url http://74.48.78.17:16666/ --report reports/dev-gate/dev-cloud-workbench-layout-live.json
+```
+
+报告字段必须能定位 `status=pass|blocked|skip`、`viewport`、`selector`、
+`failureType` 和 artifact 路径。当前允许的 `failureType` 包括 `overlap`、
+`covered-hit-target`、`overflow`、`outer-scroll-regression`、`screenshot-diff`
+以及未上线覆盖项的 `skip`。脚本会保存右侧面板、M3 控制表单、Code Agent
+输入区和 `/gate` 当前页局部截图，但不做整页像素 diff 门禁。
+
+#287 的硬件状态标签化和 #288 的 `/gate` 单一大表如果尚未上线，layout smoke
+只能把对应覆盖项记录为 `skip`，同时继续检查当前可见容器的溢出、遮挡和外层
+滚动。该 UI smoke 只能证明布局/可点击性护栏通过，不等于 M3 DEV-LIVE 硬件
+闭环通过，也不能替代 #227 的 DO/DI 功能验收。
+
 ## Stable Sources
 
 - [pikasTech/HWLAB#99](https://github.com/pikasTech/HWLAB/issues/99): default
   Cloud Workbench direction.
+- [pikasTech/HWLAB#273](https://github.com/pikasTech/HWLAB/issues/273):
+  Playwright layout/overlap smoke guardrail.
 - [pikasTech/HWLAB#108](https://github.com/pikasTech/HWLAB/issues/108): no
   outer scroll, Chinese UI, internal Markdown help.
 - [code-agent-chat-readiness.md](code-agent-chat-readiness.md): Code Agent