Every docs entry is a Markdown/MDX file in the `docs` collection. Five frontmatter
fields are recognized; `title`, `description`, and `order` are mandatory, while
`menu` and `toc` are optional and drive the page's column layout.

## Fields

| Field         | Type      | Default | Purpose                                              |
| ------------- | --------- | ------- | ---------------------------------------------------- |
| `title`       | `string`  | —       | Page title (heading, `<title>`, search, nav).        |
| `description` | `string`  | —       | Meta description and search summary.                 |
| `order`       | `number`  | —       | Global reading order (sort, prev/next, `llms.txt`).  |
| `menu`        | `string`  | —       | Left column: id of a menu to render, or nothing.     |
| `toc`         | `boolean` | `true`  | Right column: whether the on-this-page rail renders. |

## Adaptive layout

Each column is decided by its own field, and each field owns one side: the
on-this-page outline always occupies the right rail, and the left column is
reserved for navigation between pages. There are no global defaults — layout is
decided per page:

| `menu`        | `toc`   | Left column | Right column | Columns |
| ------------- | ------- | ----------- | ------------ | ------- |
| —             | `true`  | —           | page TOC     | 2       |
| —             | `false` | —           | —            | 1       |
| `"<menu id>"` | `true`  | menu        | page TOC     | 3       |
| `"<menu id>"` | `false` | menu        | —            | 2       |

- **Omitting `menu`** (the default) is a two-column prose page: content plus the
  on-this-page rail.
- **`menu: "<menu id>"`** adds that [menu](/api/menu-collection) in the left
  column — three columns.
- **`toc: false`** suppresses the on-this-page outline; with no `menu` either,
  the page renders full-width.

On a three-column page the right rail is reserved even when a page has no
headings, so the content band keeps a stable width as you move between entries.

## Section landings

Author a section's landing page as an ordinary `index` file inside the section's
directory: `src/content/docs/api/index.mdx` serves at `/api`, mirroring the way
the root `src/content/docs/index.mdx` serves at `/`. Astro's collection loader
already strips the trailing `index` when it derives entry ids, so that file is
the entry `api` — the same id an `api.mdx` at the top level would get, which is
why a section can have one or the other but not both.

## Overriding rail widths

The three column widths come from CSS variables you can override:

```css
:root {
  --layout-width-override: 1280px; /* content band */
  --layout-sidebar-width-override: 280px; /* left rail */
  --layout-sidebar-width-right-override: 240px; /* right on-this-page rail */
}
```