test: 零依赖对拍测试台（可在不改 dist/ 的前提下复现 WE 行为）

tools/serve.mjs    本地静态服务 + 测试驱动注入（模拟 WE 下发用户属性、冻结动画相位、藏 canvas 取参考帧）
tools/cdp.mjs      最小 CDP 客户端（真实时间等待；--screenshot 的虚拟时间会在骨骼加载完成前就耗尽）
tools/shot.mjs     截图/取状态，就绪判据可传入
tools/diff.mjs     ffmpeg 差分：PSNR / SSIM / 平均亮度差
tools/capture.mjs  对拍矩阵：壁纸 × 分辨率 × (正常, 藏 canvas)

实测：xilian 1920x1080 spine 层贡献 mean|diff|=26.1/255，kv37 为 10.2/255，
同配置两次截图噪声底 0.68/255。

tools/shot.mjs

@@ -0,0 +1,66 @@
+// 用 CDP 截图 / 取状态（真实时间等待，见 cdp.mjs 顶部注释）。
+// 用法：node tools/shot.mjs <out.png|-> <url> <W> <H> [waitMs] [options]
+//   --wait "<js 表达式>"   就绪判据，默认为"骨骼已加载或已报错"
+//   --eval "<js>"          截图前执行的表达式（结果会打印出来）
+//   --settle <ms>          就绪后额外等待，确保至少画过一帧（默认 500）
+//   --dom                  不截图，打印 document.title 里的测试状态
+//   --extra "<edge 旗标>"  追加 Edge 旗标
+
+import { writeFile } from "node:fs/promises";
+import { resolve } from "node:path";
+import { withPage, sleep } from "./cdp.mjs";
+
+const argv = process.argv.slice(2);
+const [out, url, w, h, waitMs = "30000"] = argv;
+if (!out || !url || !w || !h) {
+  console.error('usage: node tools/shot.mjs <out.png|-> <url> <W> <H> [waitMs] [--wait js] [--eval js] [--settle ms] [--dom]');
+  process.exit(2);
+}
+const opt = (name, dflt) => {
+  const i = argv.indexOf(`--${name}`);
+  return i >= 0 ? argv[i + 1] : dflt;
+};
+const DEFAULT_WAIT = '(window.__test ? !!(window.__test.successAt || window.__test.error) : document.readyState === "complete")';
+const waitFor = opt("wait", DEFAULT_WAIT);
+const settle = Number(opt("settle", "500"));
+const domMode = argv.includes("--dom");
+const extraArgs = [];
+if (opt("extra")) extraArgs.push(opt("extra"));
+
+const result = await withPage({ width: Number(w), height: Number(h), extraArgs }, async ({ send, evaluate, consoleLines, exceptions }) => {
+  await send("Page.navigate", { url });
+
+  const deadline = Date.now() + Number(waitMs);
+  let ready = false;
+  while (Date.now() < deadline) {
+    if (await evaluate(waitFor)) { ready = true; break; }
+    await sleep(150);
+  }
+
+  const state = await evaluate('(function(){ try { return JSON.parse((document.title||"").replace(/^TESTSTATE /,"")) } catch(e){ return null } })()');
+  await sleep(settle);
+
+  if (domMode) {
+    const evalOut = opt("eval") ? await evaluate(opt("eval")) : undefined;
+    return { ready, state, evalOut, consoleLines, exceptions };
+  }
+
+  if (opt("eval")) await evaluate(opt("eval"));
+  const shot = await send("Page.captureScreenshot", { format: "png", captureBeyondViewport: false });
+  await writeFile(resolve(out), Buffer.from(shot.data, "base64"));
+  return { ready, state, consoleLines, exceptions };
+});
+
+const tag = result.ready ? "ready" : "TIMEOUT";
+if (domMode) {
+  console.log(`state=${tag}`);
+  if (result.evalOut !== undefined) console.log(`eval=${JSON.stringify(result.evalOut)}`);
+  console.log(JSON.stringify(result.state, null, 2));
+} else {
+  console.log(`${out}  ${tag}`);
+  if (result.state) console.log(`  state: ${JSON.stringify(result.state)}`);
+}
+const noisy = result.consoleLines.filter((l) => /error|warn|uncaught|fail/i.test(l));
+if (noisy.length) console.log("  console: " + noisy.slice(0, 6).join(" | "));
+if (result.exceptions.length) console.log("  exceptions: " + result.exceptions.slice(0, 4).join(" | "));
+if (!result.ready) process.exit(1);