Dev Types For URL-Encoded Underscore Route Segments Conflict With Production Types

The dev type generator emits URL-encoded path segments (e.g. `%5F`) for route folders while the production type generator emits decoded segments (`_`). This leads to mismatched `LayoutRoutes` types between `.next/dev/types` and `.next/types/routes`. The generated `.next/dev/types/validator.ts` then imports both and fails constraint checks.

1. Start the app in dev mode: `npm run dev` 2. Stop server and run the test script: `npm t` 3. Observe TS2344 errors in `.next/dev/types/validator.ts` related to `LayoutRoutes` and `%5F` vs `_`.

This script removes the stale `.next/dev/types` directory before running `tsc`. Since the production types (`.next/types`) are already correct and self-sufficient for type checking, deleting the dev-specific generated types resolves the conflict. Add `node scripts/clean-next-dev-types.js && tsc --noEmit` to your test script.

This is a workaround, not a permanent fix. It must not be run while `next dev` is active, as the dev process may recreate the directory. It also removes dev-specific route type enhancements that may be needed for editor IntelliSense. Rollback: remove the script and restore original `test` command. A proper fix should align dev and prod type generation in Next.js.