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

.github/workflows/ci.yml

@@ -18,6 +18,7 @@ jobs:
           node-version: ${{ matrix.node }}
       - run: npm install
       - run: npm test
+      - run: npm run size
 
   e2e:
     runs-on: ubuntu-latest