fix: Module doesn't provide an export named: 'jsx'

[edwinvakayil]

Fix dev JSX runtime error and vinext start RSC entry handling

Dev: react/jsx-runtime doesn't provide an export named jsx

Root optimizeDeps.include now forces pre-bundling of react, react-dom, react/jsx-runtime, and react/jsx-dev-runtime so the automatic JSX transform always resolves to a React copy that exports jsx (React 17+). Avoids the error when resolution or a duplicate React would otherwise use an older or wrong copy. README “Known limitations” documents the fix and suggests clearing node_modules/.vite and ensuring a single React 19 install if the error persists.

• vinext start: RSC entry does not export a default handler function

The prod server now accepts both RSC entry shapes: a default function (request) => Promise<Response> (raw RSC entry from build) and a default object { fetch(request) } (Workers-style entry). It uses the function when present, otherwise calls default.fetch(request). vinext start works after vinext build whether the built dist/server/index.js is the raw RSC entry or the Workers entry. Includes a unit test that starts the prod server with a fake entry exporting { fetch } and asserts the response.

Resolves #143