Document LayoutParams, which differs from RouteParams

Describe the problem

Consider src/routes/[foo]/[bar]/[baz]/+page.svelte route.

In the src/routes/[foo]/[bar]/+layout.ts's load function,

• params.foo: string
• params.bar: string
• params.baz?: string | undefined

params.baz can be accessed, but it is not documented.

---

Current documentation.

// .svelte-kit/types/src/routes/[foo]/[bar]/[baz]/$types.d.ts

import type * as Kit from '@sveltejs/kit';
 
type RouteParams = {
  foo: string;
  bar: string;
  baz: string;
}
 
export type PageServerLoad = Kit.ServerLoad<RouteParams>;
export type PageLoad = Kit.Load<RouteParams>;

---

Demo - Consider the following project structure.

.
└── src/
    └── routes/
        └── [foo]/
            └── [bar]/
                ├── [baz]/
                │   └── +page.server.js
                └── +layout.server.js

The following types are generated by SvelteKit. (partially omitted)

// .svelte-kit/types/src/routes/[foo]/[bar]/[baz]/$types.d.ts

import type * as Kit from '@sveltejs/kit';

type RouteParams = { foo: string; bar: string; baz: string }

export type PageServerLoad = Kit.ServerLoad<RouteParams, PageServerParentData, OutputData, RouteId>;

// .svelte-kit/types/src/routes/[foo]/[bar]/$types.d.ts

import type * as Kit from '@sveltejs/kit';

type RouteParams = { foo: string; bar: string }
type LayoutParams = RouteParams & { foo?: string,bar?: string,baz?: string }
// type LayoutParams = { foo: string, bar: string, baz?: string | undefined }

export type LayoutServerLoad = Kit.ServerLoad<LayoutParams, LayoutServerParentData, OutputData, LayoutRouteId>;

Describe the proposed solution

Add documentations to

• https://kit.svelte.dev/docs/types#generated-types
• https://kit.svelte.dev/docs/load

Alternatives considered

No response

Importance

nice to have

Additional Information

No response

Start with the Generated types and load documentation pages linked in the issue. Compare the documented RouteParams examples with the reported LayoutParams behavior, then explain the distinction using the provided nested-route example. Done means both documentation locations clearly describe which parameters are available to a layout load function.