The new validator doesn't work with rootDir tsconfig property

### Link to the code that reproduces this issue https://github.com/ecl1ps/next-validator-rootdir/commit/3490369c43c6d8915cb8279ec9b9cc0a86d2cb5e ### To Reproduce 1. pnpm install 2. pnpm build ### Current vs. Expected behavior The new validator breaks the build when you use rootDir and your sources are not at the top level of the repo. <img width="1556" height="602" alt="Image" src="https://github.com/user-attachments/assets/91aab968-e763-49b8-a99c-99ddbe1249d6" /> ``` > next build ▲ Next.js 15.5.1-canary.2 Linting and checking validity of types ...Failed to compile. Type error: File 'C:/data/repos/next-validator-rootdir/.next/types/validator.ts' is not under 'rootDir' 'C:/data/repos/next-validator-rootdir/src'. 'rootDir' is expected to contain all source files. The file is in the program because: Root file specified for compilation Next.js build worker exited with code: 1 and signal: null ``` It is expected to work with the rootDir. ### Provide environment information ```bash Operating System: Platform: win32 Arch: x64 Version: Windows 11 Pro Available memory (MB): 32401 Available CPU cores: 20 Binaries: Node: 24.6.0 npm: 11.5.1 Yarn: N/A pnpm: 10.0.0 Relevant Packages: next: 15.5.1-canary.2 // Latest available version is detected (15.5.1-canary.2). eslint-config-next: N/A react: 19.1.1 react-dom: 19.1.1 typescript: 5.9.2 Next.js Config: output: N/A ``` ### Which area(s) are affected? (Select all that apply) Output ### Which stage(s) are affected? (Select all that apply) next build (local) ### Additional context BTW, why don't you export types like `ApiRouteConfig`, `PagesPageConfig`, and `AppPageConfig` (which you AFAIK define only [inside the new validator](https://github.com/vercel/next.js/blob/f88de0d8f1b8ec508b7cfef6abfaaa32e72e690c/packages/next/src/server/lib/router-utils/typegen.ts#L435)). We could use them to type our pages and API routes and get the validation even earlier, in the IDE. This was a breaking change …