radix-ui package exports map prevents resolving package.json

## Bug report

### Current Behavior

The unified `radix-ui` package's exports map has a `"./*"` wildcard that maps to `./dist/*`. This intercepts attempts to resolve `radix-ui/package.json`, causing Node.js to look for `./dist/package.json.mjs` instead of the actual file at the package root.

Tools that use `require.resolve('radix-ui/package.json')` to read package metadata fail. For example, Storybook's compatibility checker emits:

```
▲  unable to find package.json for radix-ui
```

### Expected behavior

`require.resolve('radix-ui/package.json')` should resolve to the package's `package.json` file, as is conventional for npm packages with exports maps. 

From the NodeJS docs: https://nodejs.org/api/packages.html#package-entry-points

> Existing packages introducing the ["exports"](https://nodejs.org/api/packages.html#exports) field will prevent consumers of the package from using any entry points that are not defined, including the [package.json](https://nodejs.org/api/packages.html#nodejs-packagejson-field-definitions) (e.g. require('your-package/package.json')). This will likely be a breaking change.

### Reproducible example

```js
 // Node.js 22+
require.resolve('radix-ui/package.json')
// => Error: Cannot find module 'radix-ui/dist/package.json.js'
```

This can also be reproduced by running Storybook in any project that depends on `radix-ui`.

### Suggested solution

Add a `./package.json` entry to the exports map in `packages/radix-ui/package.json`:
https://github.com/radix-ui/primitives/blob/main/packages/react/radix-ui/package.json#L16

```json
{
  "exports": {
    ".": { ... },
    "./*": { ... },
    "./package.json": "./package.json"
  }
}
  ```

### Additional context

The individual `@radix-ui/react-*` packages don't have this issue because they either lack an exports map or don't use a `"./*"` wildcard that intercepts `./package.json`.

### Your environment

| Software         | Version |
|------------------|---------|
| radix-ui         | 1.4.3   |
| Node.js         | 22.x    |
| Storybook     | 10.2.12 |

[]