test(evals): accept LayoutProps in App Router migration (#98365)
### What?
Updates the App Router migration eval to accept the generated
LayoutProps helper as valid typing for root layout children.
### Why?
The current docs support both an inline ReactNode annotation and the
globally available LayoutProps helper. Opus 5 followed that guidance in
all four AGENTS.md runs, but the eval rejected LayoutProps and reported
a false regression.
### How?
The assertion still requires children and now accepts either documented
type form.
### Testing
- Prettier check
- ESLint
- Focused assertion check covering both valid forms and an untyped
invalid form
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