test(sw): the silent-update case rewrites the served worker, so it runs alone

Simulating a deploy means rewriting dist/sw.js, which the whole origin shares:
run beside other cases it replaced their service worker mid-test and wiped the
cache under them (an editor mid-load could no longer fetch spell.wasm, and the
cache-first case stopped seeing its cached asset). It is @serial now, and it
skips where the served files are not on this disk -- the Docker image reported
exactly that as ENOENT.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: chaxus

docs/explorations/2026-08-22-stale-build-and-panel-flash.md

@@ -121,6 +121,15 @@ Qjgbc rgjc / Qjgbc qs`rgjc / Ajgai rm_bb l mrcq
 | `test/unit/update-prompt.test.ts` 五条（出现一次、点刷新会 SKIP_WAITING、接管后 reload 一次、超时兜底、忽略不动 worker） | —                                                                                              |
 | `test/e2e/entry-paths.spec.ts` 的"the home-state panel never shows while a named document loads"（从首帧起连采 12 次）   | 去掉 `opening-document` 那一行 → 用例报 `the panel was painted while the document was loading` |
 
+### 这条用例必须 `@serial`
+
+第一版没打标签，CI 里连带弄红了同分片的另外两条。原因是它"模拟部署"的手段是改写
+**整个源站共用的** `dist/sw.js`：并行跑时别的用例的 worker 也会被换掉，缓存在它们
+脚下被清空——一个正在加载的编辑器于是取不到 `spell.wasm`，`sw-vendor-cache-first`
+也看不到自己缓存的资源。打上 `@serial` 之后它只在单 worker 那一趟跑；Docker 与
+Pages 两趟本来就 `--grep-invert @serial`，而且那里的文件根本不在本机磁盘上
+（Docker 那次报的就是 `ENOENT: dist/sw.js`），所以再加一条"文件不在就 skip"。
+
 ## 给下一个人
 
 - 面板默认可见这件事本身是个坑：任何新的"启动时决定开什么"的入口（新的 query 参数、

test/e2e/sw-silent-update.spec.ts

@@ -1,4 +1,4 @@
-import { readFileSync, writeFileSync } from 'node:fs';
+import { existsSync, readFileSync, writeFileSync } from 'node:fs';
 import { resolve } from 'node:path';
 import { expect, test } from './lib/l0';
 import { settleEditor } from './lib/visual';
@@ -20,6 +20,13 @@ import { settleEditor } from './lib/visual';
  * The test deploys a second build the only way a static preview can: it
  * rewrites the vendor stamp inside the served sw.js, which is exactly what
  * bin/build.sh does when the vendored tree changes.
+ *
+ * That rewrite is visible to the whole origin, so this case is `@serial`: run
+ * beside others it replaces THEIR service worker mid-test too, which wipes the
+ * cache under them (an editor mid-load then fails to fetch spell.wasm, and the
+ * cache-first case stops seeing its cached asset). It is skipped where the
+ * served files are not on this disk -- the Docker image and any run against a
+ * deployed site.
  */
 const PORT = process.env.E2E_PORT ?? '4173';
 const OUT_DIR = process.env.E2E_PORT ? `dist-e2e-${PORT}` : 'dist';
@@ -38,8 +45,11 @@ const controllerVendorVersion = (page: import('@playwright/test').Page) =>
     });
   });
 
-test.describe('a stale build heals itself', () => {
+test.describe('a stale build heals itself @serial', () => {
   test.describe.configure({ timeout: 240_000 });
+  // The container and a deployed site serve their own copy; there is nothing
+  // here to rewrite, and no way to deploy a second build mid-run.
+  test.skip(!existsSync(SW_PATH), 'needs the locally built site this run is serving');
 
   let original = '';
   test.beforeAll(() => {