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/lib/dev.js

@@ -4,17 +4,18 @@
 
 import { createServer } from 'node:http'
 
-import bankaiPlugin, { CLIENT_URL } from './plugin.js'
+import bankaiPlugin, { findCss, CLIENT_URL } from './plugin.js'
 import { resolveApp } from './app.js'
 import { documentHead, documentTail } from './document.js'
 
 export default async function dev ({ entry, port = 8080, title = 'choo' }) {
   const { createServer: createViteServer } = await import('vite')
+  const css = await findCss(entry) // style.css convention; restart to add it
 
   const vite = await createViteServer({
     appType: 'custom',
     server: { middlewareMode: true },
-    plugins: [bankaiPlugin(entry)],
+    plugins: [bankaiPlugin(entry, { css })],
     logLevel: 'warn'
   })
 
@@ -26,14 +27,22 @@ export default async function dev ({ entry, port = 8080, title = 'choo' }) {
         const app = resolveApp(mod, entry)
         const state = {}
 
+        // Read the first chunk before writing the head: by then stores
+        // have run and the view has rendered up to its first async hole,
+        // so DOMTitleChange emits have landed in state.title.
+        const reader = app.toStream(req.url, state).getReader()
+        const first = await reader.read()
+
         res.writeHead(200, { 'content-type': 'text/html; charset=utf-8' })
         res.write(documentHead({
-          title,
+          title: state.title || title,
           scripts: ['/@vite/client', CLIENT_URL]
         }))
-
-        for await (const chunk of app.toStream(req.url, state)) {
-          res.write(chunk)
+        if (!first.done) res.write(first.value)
+        for (;;) {
+          const { done, value } = await reader.read()
+          if (done) break
+          res.write(value)
         }
         res.end(documentTail(state))
       } catch (err) {