Lint no-head-element for App Router since it will cause hydrated problems

[sanmaopep]

Goals

1. lint no-head-element for AppRouter

Non-Goals

Background

In AppRouter, when ai add in layout.tsx, it will throws a 403 React Error which indicates the hydrated conflict btw Next metadata and contents in .

Proposal

For AppRouter, lint warn or error for element, and return message that tell user or ai to use metadata (https://nextjs.org/docs/app/api-reference/functions/generate-metadata#unsupported-metadata) instead