"type[UnionType]" is not assignable to "type"

**Describe the bug**
Pyright rejects assigning `UnionType` to a type variable, although `UnionType` is a valid type object.

**Minimal repro:**

```python
from types import UnionType
_: type = UnionType
```

```bash
> pyright test.py
error: Type "type[UnionType]" is not assignable to declared type "type" (reportAssignmentType)
```

**Environment**

* Reproduced with Pyright CLI version **1.1.403**
* Also reproduced on `main` (commit: `e32022ce6b12c74aca5cb00b267bda81995f3b86`)
* [Playground link](https://pyright-play.net/?pyrightVersion=1.1.403&code=GYJw9gtgBALgngBwKYGcoEsILCGUCqAdumIQCqJIBQoksi6hA5hljngIKFxVUD6ALnrIoAXgLFSFZEA)

Start by reproducing the issue in test.py with the Pyright CLI, using version 1.1.403 or the referenced main commit. Trace how assignment compatibility handles the `type[UnionType]` expression. Done means the example no longer produces reportAssignmentType while existing type-checking behavior remains intact.

Written by the indexing model from the issue text.