1.4.1: nested pages dirs, CommonJS require of react in client bundles

- Page URL paths are now relative to src/pages. The old greedy
  `.*/pages/` cut mapped src/pages/admin/pages/index.tsx to /index, so
  every page under a nested `pages` directory collided with the home page
  and was never bundled. SSR also tells API routes by URL path now.
- CommonJS `require("react…")` in client bundles (for example
  use-sync-external-store/shim, pulled in by MUI) threw "Dynamic require
  of "react" is not supported" in the browser. Those requires now go
  through a small bundled ESM module that imports the external.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

dist/functions/bundler/pages-ssr-context-bundler.js

@@ -46,7 +46,7 @@ async function computeEntryToPage() {
     }
     catch (error) { }
     for (const page of pages) {
-        if (page.local_path.match(/\/pages\/api\//) ||
+        if (page.url_path.startsWith("/api/") ||
             page.local_path.match(/\.server\.tsx?$/)) {
             const ts = await Bun.file(page.local_path).text();
             if (ts.match(/(export default)|(export \w+ handler)|(export \w+ server)/)) {