feat(examples)+test(e2e): counter service worker; bankai dev+prod in Chromium

The counter example gains a sw.js exercising bankai's injected-precache
build. e2e proves both bankai paths in real Chromium: the built app
serves, hydrates and runs with zero console errors and zero mismatch
warnings (and choo consumed window.initialState), and the dev server's
Vite-transformed virtual entry hydrates the same way.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014NgfSjHE11oFpoSnLVKLXd

examples/counter/sw.js

@@ -0,0 +1,28 @@
+/* global __BANKAI_ASSETS__ */
+// Service worker built by `bankai build`: the precache list is injected
+// at build time from the asset manifest (the choo-service-worker
+// convention, manifest edition). Register it from your app with
+// navigator.serviceWorker.register('/sw.js').
+
+const CACHE = 'counter-v1'
+const ASSETS = __BANKAI_ASSETS__
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE).then((cache) => cache.addAll(ASSETS))
+  )
+})
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys().then((keys) =>
+      Promise.all(keys.filter((k) => k !== CACHE).map((k) => caches.delete(k)))
+    )
+  )
+})
+
+self.addEventListener('fetch', (event) => {
+  event.respondWith(
+    caches.match(event.request).then((hit) => hit || fetch(event.request))
+  )
+})

test/e2e/bankai.test.js

@@ -0,0 +1,72 @@
+// bankai v10 end-to-end in real Chromium: the production pipeline
+// (build → serve → SSR page hydrates and runs) and the dev server
+// (Vite middleware + virtual entry + streaming SSR).
+
+import { test, before, after } from 'node:test'
+import assert from 'node:assert'
+import { mkdtemp, rm } from 'node:fs/promises'
+import { join, dirname } from 'node:path'
+import { tmpdir } from 'node:os'
+import { fileURLToPath } from 'node:url'
+import { chromium } from 'playwright'
+
+import build from '../../packages/bankai/lib/build.js'
+import serve from '../../packages/bankai/lib/serve.js'
+import dev from '../../packages/bankai/lib/dev.js'
+
+const repo = join(dirname(fileURLToPath(import.meta.url)), '..', '..')
+const entry = join(repo, 'examples', 'counter', 'app.js')
+
+let browser, outDir, prod, devSrv
+
+before(async () => {
+  browser = await chromium.launch()
+  outDir = await mkdtemp(join(tmpdir(), 'bankai-e2e-'))
+  await build({ entry, outDir, title: 'counter' })
+  prod = await serve({ outDir, port: 0 })
+  devSrv = await dev({ entry, port: 0, title: 'counter dev' })
+})
+
+after(async () => {
+  await browser?.close()
+  await prod?.close()
+  await devSrv?.close()
+  if (outDir) await rm(outDir, { recursive: true, force: true })
+})
+
+async function openAndCount (origin) {
+  const page = await browser.newPage()
+  const errors = []
+  const warnings = []
+  page.on('console', (msg) => {
+    if (msg.type() === 'error') errors.push(msg.text())
+    if (msg.type() === 'warning') warnings.push(msg.text())
+  })
+  page.on('pageerror', (err) => errors.push(String(err)))
+
+  await page.goto(origin + '/')
+  await page.waitForFunction(() => document.querySelector('h1')?.textContent === 'count is 0')
+
+  await page.click('button')
+  await page.waitForFunction(() => document.querySelector('h1')?.textContent === 'count is 1')
+
+  return { page, errors, warnings }
+}
+
+test('production: built app serves, hydrates and runs with no errors', async () => {
+  const { page, errors, warnings } = await openAndCount(prod.origin)
+
+  assert.deepStrictEqual(errors, [], 'no console errors')
+  const mismatches = warnings.filter((w) => w.includes('markup differ'))
+  assert.deepStrictEqual(mismatches, [], 'no hydration mismatch warnings')
+
+  const state = await page.evaluate(() => window.choo ? 'devtools' : typeof window.initialState)
+  assert.strictEqual(state, 'undefined', 'choo consumed initialState (deleted after merge)')
+  await page.close()
+})
+
+test('dev server: Vite-transformed entry hydrates and runs', async () => {
+  const { page, errors } = await openAndCount(devSrv.origin)
+  assert.deepStrictEqual(errors, [], 'no console errors')
+  await page.close()
+})