Improve no response route handler error (#89036)
## Improve route handler "no response" error message for debugging
### What?
Improves the error message thrown when an app route handler doesn't
return a `Response` object to include additional debugging information:
- **The actual type received** - Shows whether it was `null`,
`undefined`, or the constructor name for objects
- **The HTTP method** - e.g., `GET`, `POST`
- **The URL pathname** - The route being requested
### Why?
When debugging intermittent prerender failures like:
```
Error: No response is returned from route handler '[project]/apps/web/app/favicon--route-entry.js'.
```
It was unclear what the handler actually returned. This made it
difficult to diagnose whether:
- The handler returned `undefined` (didn't return anything)
- The handler returned `null` (explicit null)
- The handler returned some other object type (module loading issue)
### How?
Updated the error message format from:
```
No response is returned from route handler '/path/route.ts'. Ensure you return a `Response` or a `NextResponse` in all branches of your handler.
```
To:
```
No response is returned from route handler '/path/route.ts'. Expected a Response object but received 'undefined' (method: GET, url: /favicon.ico). Ensure you return a `Response` or a `NextResponse` in all branches of your handler.
```
### Changes
- `packages/next/src/server/route-modules/app-route/module.ts` -
Enhanced error with type detection and request context
- `packages/next/errors.json` - Updated error template
- `test/e2e/app-dir/app-routes/app-custom-routes.test.ts` - Updated test
to match new error format
