feat(bankai): Phase 4 follow-ups — css convention, live titles, prerender, HTTP/2, size budget

- style.css convention: <entry dir>/style.css is imported by the virtual
  client entry (CSS is a client concern; server code never sees it — the
  v8 answer to sheetify), extracted and hashed by Vite, stylesheet-linked
  in the head and preloaded via Early Hints. Counter example styled.
- SSR <title> from state: the server reads the first stream chunk before
  writing the head, by which point stores and the first render slice have
  run — DOMTitleChange emits land in the document title. Counter emits.
- bankai build --prerender /,/about renders routes through the same
  toStream path to static <route>/index.html (precompressed, precached
  by the service worker, served with Early Hints).
- bankai serve --h2: HTTP/2 with a generated local cert (openssl,
  cached; allowHTTP1) — browsers only act on Early Hints over h2/h3.
  Tested with a real h2 client observing the 103 interim response.
- npm run size: the framework wire-size budget, enforced in CI. Whole
  framework (core + html engine + morph + hydrate) is 7.97 kB min+gzip /
  7.15 kB brotli; budget 8.5 kB with the v7 '4kb' context documented
  (that number excluded the html engine, which lived in the browserify
  transform).

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

packages/bankai/test/build-serve.test.js

@@ -16,11 +16,11 @@ import serve from '../lib/serve.js'
 const repo = join(dirname(fileURLToPath(import.meta.url)), '..', '..', '..')
 const entry = join(repo, 'examples', 'counter', 'app.js')
 
-let outDir, meta, srv
+let outDir, meta, prerendered, srv
 
 before(async () => {
   outDir = await mkdtemp(join(tmpdir(), 'bankai-test-'))
-  ;({ meta } = await build({ entry, outDir, title: 'counter' }))
+  ;({ meta, prerendered } = await build({ entry, outDir, title: 'counter', prerender: ['/'] }))
   srv = await serve({ outDir, port: 0 })
 })
 
@@ -58,16 +58,38 @@ test('build produced manifest, metadata and precompressed assets', async () => {
   await access(join(outDir, chunk.slice(1) + '.gz'))
 })
 
-test('pages get 103 Early Hints carrying the route assets', async () => {
+test('the style.css convention bundles css the server never imports', async () => {
+  assert.strictEqual(meta.assets.css.length, 1, 'extracted css asset')
+  const res = await get('/some/page')
+  const text = res.body.toString()
+  assert.match(text, /<link rel="stylesheet" href="\/assets\/.*\.css">/)
+  assert.match(String(res.headers.link), /as=style/, 'stylesheet in the Link header')
+})
+
+test('prerendered routes are written and served statically with hints', async () => {
+  assert.deepStrictEqual(prerendered, ['/'])
+  await access(join(outDir, 'index.html'))
   const res = await get('/')
+  assert.strictEqual(res.status, 200)
+  assert.match(res.body.toString(), /count is 0/)
+  assert.strictEqual(res.interim[0]?.statusCode, 103, 'prerendered pages still send Early Hints')
+})
+
+test('the SSR <title> comes from state (DOMTitleChange during render)', async () => {
+  const res = await get('/some/page')
+  assert.match(res.body.toString(), /<title>count is 0<\/title>/)
+})
+
+test('live pages get 103 Early Hints carrying the route assets', async () => {
+  const res = await get('/some/page')
   assert.strictEqual(res.interim.length, 1, 'one interim response')
   assert.strictEqual(res.interim[0].statusCode, 103)
   assert.match(String(res.interim[0].headers.link), /rel=modulepreload/)
   assert.match(String(res.headers.link), /rel=modulepreload/, 'Link header repeated on the final response')
 })
 
-test('pages stream SSR html with a filtered initialState tail', async () => {
-  const res = await get('/')
+test('live pages stream SSR html with a filtered initialState tail', async () => {
+  const res = await get('/some/page')
   const text = res.body.toString()
   assert.strictEqual(res.status, 200)
   assert.match(text, /<h1>count is 0<\/h1>/, 'server-rendered view')
@@ -76,6 +98,38 @@ test('pages stream SSR html with a filtered initialState tail', async () => {
   assert.ok(!/initialState=.*"events"/.test(text), 'internals filtered from state')
 })
 
+test('h2: HTTP/2 server sends Early Hints and streams the page', async (t) => {
+  const { default: http2 } = await import('node:http2')
+  let h2srv
+  try {
+    h2srv = await serve({ outDir, port: 0, h2: true })
+  } catch (err) {
+    t.skip('openssl unavailable: ' + err.message)
+    return
+  }
+
+  const session = http2.connect(`https://localhost:${h2srv.port}`, { rejectUnauthorized: false })
+  const result = await new Promise((resolve, reject) => {
+    const req = session.request({ ':path': '/some/page' })
+    let interim = null
+    let status = null
+    let body = ''
+    req.on('headers', (headers) => { interim = headers })
+    req.on('response', (headers) => { status = headers[':status'] })
+    req.on('data', (d) => { body += d })
+    req.on('end', () => resolve({ interim, status, body }))
+    req.on('error', reject)
+    req.end()
+  })
+  session.close()
+  await h2srv.close()
+
+  assert.strictEqual(result.status, 200)
+  assert.strictEqual(result.interim?.[':status'], 103, '103 interim over h2')
+  assert.match(String(result.interim?.link), /rel=modulepreload/)
+  assert.match(result.body, /count is 0/)
+})
+
 test('hashed assets are immutable and served precompressed on request', async () => {
   const chunk = meta.assets.scripts[0]