Cloudflare workerd SSR: React module duplication in HeadContent useContext when used with TanStack Start + @cloudflare/vite-plugin

## Setup

- `vite-plus` (alias `vite` → `@voidzero-dev/vite-plus-core`) `0.1.22`
- `@cloudflare/vite-plugin` `^1.37.2` (workerd SSR environment)
- `@tanstack/react-start` `^1.168.10` + `@tanstack/react-router` `^1.170.7`
- React 19, `@vitejs/plugin-react` `^6.0.2`
- bun workspaces, single app uses TanStack Start

`vite.config.ts` mirrors the working garden setup exactly (vanilla Vite 8 + same `environments.ssr.optimizeDeps.include` list + same plugin order):

\`\`\`ts
export default defineConfig({
resolve: { tsconfigPaths: true, dedupe: ["react", "react-dom"] },
environments: {
ssr: {
optimizeDeps: {
include: [
"react", "react/jsx-runtime", "react/jsx-dev-runtime",
"react-dom", "react-dom/server",
"@tanstack/react-router > @tanstack/react-store",
],
},
},
},
plugins: [
cloudflare({ viteEnvironment: { name: "ssr" } }),
agents(),
tailwindcss(),
tanstackStart(),
viteReact(),
],
});
\`\`\`

## What happens

SSR shell render of \`HeadContent\` crashes with React invalid-hook-call:

\`\`\`
TypeError: Cannot read properties of null (reading 'useContext')
at exports.useContext (deps_ssr/react.js?v=…:706)
at useRouter (@tanstack/react-router/src/useRouter.tsx:20)
at useTags (@tanstack/react-router/src/headContentUtils.tsx:213)
at HeadContent (@tanstack/react-router/src/HeadContent.dev.tsx:22)
\`\`\`

i.e. the classic two-copies-of-React-in-workerd-SSR situation that cloudflare/workers-sdk#11825 describes. Browser ends up on the JSON 500 page (\`{"status":500,"message":"HTTPError"}\`).

The exact same source tree + the exact same config, run on **vanilla Vite 8** in another project (https://github.com/voidzero-dev/garden parallel — its \`apps/web\` works fine), renders cleanly.

## Comparison

| | vanilla Vite 8 (garden) | vite-plus-core 0.1.22 (this repo) |
|---|---|---|
| Same vite.config | works | 500 with useContext null in HeadContent |
| Same plugin order | works | broken |
| Same SSR optimizeDeps.include | works | broken |

Switching this repo's catalog alias to vanilla Vite 8 doesn't fully fix it either — first \`/\` render works, but on any subsequent SSR render of the route (HMR reload, client navigate, etc.) the same useContext null surfaces.

## Suspicion

`@voidzero-dev/vite-plus-core` ships its own (rolldown-backed?) Vite that handles \`environments.ssr.optimizeDeps\` differently from upstream Vite's dep optimizer, so the React module the workerd runner ends up with isn't the same instance the route bundle imports. This trips every provider hook downstream (`useContext` in `HeadContent`, `useEffect` in `QueryClientProvider`, etc.).

Repro repo: I can put one up if helpful — but the diff against the existing TanStack Start cloudflare example is essentially "swap upstream Vite for the vite-plus-core alias and add `@cloudflare/vite-plugin`".

## Related

- https://github.com/cloudflare/workers-sdk/issues/11825
- https://github.com/TanStack/router/issues/5208

Reproduisez l’échec avec le vite.config.ts fourni et la configuration SSR TanStack Start Cloudflare, puis comparez-le avec l’exemple garden fonctionnel de vanilla Vite 8. Commencez par suivre environments.ssr.optimizeDeps et le chargement des modules SSR de workerd, en vous concentrant sur la question de savoir si React est instancié deux fois. Le travail est considéré comme terminé lorsque HeadContent et les rendus SSR suivants s’exécutent sans l’erreur invalid-hook-call.

Rédigé par le modèle d'indexation à partir du texte de l'issue.