This JSX tag's 'children' prop expects type 'string' which requires multiple children, but only a single child was provided

// JSX typing is based fully on React 19 typings, but simplified to minimal reproducible example
// Exactly the same error occurs with React typings
// (https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/react/index.d.ts)
export declare function createElement(
sel: any,
data?: any,
text?: any
): JSX.Element;

export declare const Fragment: (props: {
children?: JSX.Element;
}) => JSX.Element;

export namespace JSX {
export type Element =
| string
| number
| bigint
| Iterable
| boolean
| null
| undefined;
export interface ElementAttributesProperty {}
export interface ElementChildrenAttribute { children?: Element;}
export interface IntrinsicAttributes {}
export interface IntrinsicElements { div: { id?: string };}
}
```

### 🙁 Actual behavior

Calling JSX component that accepts `string` children type emits the following error:
> This JSX tag's 'children' prop expects type 'string' which requires multiple children, but only a single child was provided.ts(2745)

### 🙂 Expected behavior

No error should be emitted

### Additional information about the issue

**The exact same error is reproducible with official React 19 typings**. See tiny reproduction repository: https://github.com/maxpatiiuk/typescript-react-19-jsx-bug

---

Looking at https://github.com/microsoft/TypeScript/blob/main/src/compiler/checker.ts, the error is triggered by the following check:

```ts
// Line 21585:
else if (!isTypeRelatedTo(getIndexedAccessType(source, childrenNameType), childrenTargetType, relation)) {
// arity mismatch
result = true;
const diag = error(
containingElement.openingElement.tagName,
Diagnostics.This_JSX_tag_s_0_prop_expects_type_1_which_requires_multiple_children_but_only_a_single_child_was_provided,
childrenPropName,
typeToString(childrenTargetType),
);
if (errorOutputContainer && errorOutputContainer.skipLogging) {
(errorOutputContainer.errors || (errorOutputContainer.errors = [])).push(diag);
}
}
```

It appears that `getIndexedAccessType(source, childrenNameType)` tries to get the indexed type of `string`, which returns `unknown` type, which is not considered related to `string` type.

---

Potentially related to https://github.com/microsoft/TypeScript/issues/60572, however the suggested workaround in that issue is not working.