build fails with custom root

[hi-ogawa]

Found while testing in hi-ogawa/rscpress#31, which uses a programmatic build with custom root createBuilder({ root: "docs", ... }).

node:fs:2425
    return binding.writeFileUtf8(
                   ^

Error: ENOENT: no such file or directory, open 'dist/ssr/__vite_rsc_assets_manifest.js'
    at Object.writeFileSync (node:fs:2425:20)
    at writeAssetsManifest (file:///home/hiroshi/code/personal/rscpress/node_modules/.pnpm/@vitejs+plugin-rsc@0.4.20_react-dom@19.1.1_react@19.1.1__react@19.1.1_vite@7.1.1_@types+node@24.2.1_yaml@2.8.1_/node_modules/@vitejs/plugin-rsc/dist/plugin-DYOxE_xg.js:506:7)
    at BasicMinimalPluginContext.buildApp (file:///home/hiroshi/code/personal/rscpress/node_modules/.pnpm/@vitejs+plugin-rsc@0.4.20_react-dom@19.1.1_react@19.1.1__react@19.1.1_vite@7.1.1_@types+node@24.2.1_yaml@2.8.1_/node_modules/@vitejs/plugin-rsc/dist/plugin-DYOxE_xg.js:500:3)
    at async Object.buildApp (file:///home/hiroshi/code/personal/rscpress/node_modules/.pnpm/vite@7.1.1_@types+node@24.2.1_yaml@2.8.1/node_modules/vite/dist/node/chunks/dep-eRCq8YxU.js:34717:5)
    at async file:///home/hiroshi/code/personal/rscpress/repro.ts:23:1 {
  errno: -2,
  code: 'ENOENT',
  syscall: 'open',
  path: 'dist/ssr/__vite_rsc_assets_manifest.js'
}

Node.js v22.18.0