docs(layouts): rework the layout section, add default layout

docs/content/2.guide/3.directory-structure/6.layouts.md

@@ -8,53 +8,65 @@ head.title: Layouts directory
 
 Nuxt provides a customizable layouts framework you can use throughout your application, ideal for extracting common UI or code patterns into reusable layout components.
 
-Layouts are placed in the `layouts/` directory and will be automatically loaded via asynchronous import when used. Layouts are used by setting a `layout` property as part of your page metadata (if you are using the `~/pages` integration), or by using the `<NuxtLayout>` component. (**Note**: The layout name is normalized to kebab-case, so `someLayout` becomes `some-layout`.)
+Layouts are placed in the `layouts/` directory and will be automatically loaded via asynchronous import when used. Layouts are used by adding `<NuxtLayout>` to your `app.vue`, and either setting a `layout` property as part of your page metadata (if you are using the `~/pages` integration), or by manually specifying it as a prop to `<NuxtLayout>`. (**Note**: The layout name is normalized to kebab-case, so `someLayout` becomes `some-layout`.)
 
 If you only have a single layout in your application, we recommend using [app.vue](/guide/directory-structure/app) instead.
 
 ::alert{type=warning}
 Unlike other components, your layouts must have a single root element to allow Nuxt to apply transitions between layout changes - and this root element cannot be a `<slot />`.
 ::
 
-## Example: Enabling layouts with `app.vue`
+## Enabling the default layout
 
-```bash
--| layouts/
----| custom.vue
--| app.vue
-```
+Add a `~/layouts/default.vue`:
 
-In your layout files, you'll need to use `<slot />` to define where the content of your layout will be loaded. For example:
-
-```vue{}[layouts/custom.vue]
+```vue [layouts/default.vue]
 <template>
   <div>
-    Some shared layout content:
+    Some default layout shared across all pages
     <slot />
   </div>
 </template>
 ```
 
-Here's how you might use that layout in `app.vue`:
+In a layout file, the content of the layout will be loaded in the `<slot />`, rather than using a special component.
 
-```vue{}[app.vue]
+If you use a `app.vue` you will also need to add `<NuxtLayout>`:
+
+```vue [app.vue]
 <template>
-  <NuxtLayout name="custom">
-    Hello world!
+  <NuxtLayout>
+    some page content
   </NuxtLayout>
 </template>
 ```
 
-## Example: setting the layout with `~/pages`
+## Setting another layout
 
 ```bash
 -| layouts/
+---| default.vue
 ---| custom.vue
--| pages/
----| index.vue
 ```
 
-You can set your layout within your page components like this:
+You can directly override the default layout like this:
+
+```vue{}[app.vue]
+<template>
+  <NuxtLayout :name="layout">
+    <NuxtPage />
+  </NuxtLayout>
+</template>
+
+<script setup>
+// You might choose this based on an API call or logged-in status
+const layout = "custom";
+</script>
+```
+
+Alternatively, you can override the default layout per-page like this:
+
+::code-group
 
 ```vue{}[pages/index.vue]
 <script>
@@ -65,8 +77,6 @@ definePageMeta({
 </script>
 ```
 
-And in your `app.vue` you need to wrap the `NuxtPage` component with the `NuxtLayout` component.
-
 ```vue{}[app.vue]
 <template>
   <NuxtLayout>
@@ -75,56 +85,31 @@ And in your `app.vue` you need to wrap the `NuxtPage` component with the `NuxtLa
 </template>
 ```
 
-::alert{type=info}
-Learn more about [defining page meta](/guide/directory-structure/pages#page-metadata).
-::
-
-## Example: manual control with `~/pages`
-
-Even if you are using the `~/pages` integration, you can take full control by using the `<NuxtLayout>` component (which is globally available throughout your application), by setting `layout: false`.
-
-::code-group
-
 ```vue [layouts/custom.vue]
 <template>
   <div>
-    <header>
-      <slot name="header">
-        Default header content
-      </slot>
-    </header>
-    <main>
-      <slot />
-    </main>
+    Some *custom* layout
+    <slot />
   </div>
 </template>
 ```
 
-```vue [pages/index.vue]
+```vue [layouts/default.vue]
 <template>
   <div>
-    <NuxtLayout name="custom">
-      <template #header> Some header template content. </template>
-
-      The rest of the page
-    </NuxtLayout>
+    A *default* layout
+    <slot />
   </div>
 </template>
-
-<script setup>
-definePageMeta({
-  layout: false,
-});
-</script>
 ```
 
 ::
 
-::alert{type=warning}
-If you use `<NuxtLayout>` within your pages, make sure it is not the root element (or disable layout/page transitions).
+::alert{type=info}
+Learn more about [defining page meta](/guide/directory-structure/pages#page-metadata).
 ::
 
-## Example: changing the layout
+## Changing the layout dynamically
 
 You can also use a ref or computed property for your layout.
 
@@ -147,3 +132,48 @@ definePageMeta({
 ```
 
 :LinkExample{link="/examples/routing/layouts"}
+
+## Overriding a layout on a per-page basis
+
+If you are using the `~/pages` integration, you can take full control by setting `layout: false` and then using the `<NuxtLayout>` component within the page.
+
+::code-group
+
+```vue [pages/index.vue]
+<template>
+  <div>
+    <NuxtLayout name="custom">
+      <template #header> Some header template content. </template>
+
+      The rest of the page
+    </NuxtLayout>
+  </div>
+</template>
+
+<script setup>
+definePageMeta({
+  layout: false,
+});
+</script>
+```
+
+```vue [layouts/custom.vue]
+<template>
+  <div>
+    <header>
+      <slot name="header">
+        Default header content
+      </slot>
+    </header>
+    <main>
+      <slot />
+    </main>
+  </div>
+</template>
+```
+
+::
+
+::alert{type=warning}
+If you use `<NuxtLayout>` within your pages, make sure it is not the root element (or disable layout/page transitions).
+::