`list[str]` is assignable to `list[int | Any]`, but shouldn't be

[Playground](https://pyright-play.net/?pythonVersion=3.13&strict=true&locale=en&enableExperimentalFeatures=true&code=GYJw9gtgBALgngBwJYDsDmUkQWEMoCCKcAsAFDkAmApsFMABQAeAXFADZIDOMA2qvgA%2BhYgF0AlC3JQZUBAEMuXclVpQ0zNpx68eICVLKz6zcUA):

```python
from typing import Any

def f(x: list[int | Any]):
pass

def g(x: list[str]):
f(x)
```

Pyright allows this, but I would expect it to error, since there is no materialization of `list[int | Any]` that is a supertype of `list[str]`. Mypy errors here correctly.

Use case: Dicts support `.update()` with keyword args, like `{}.update(a=3)`. Currently typeshed allows this only if the key type is `str`. I got an error on a dict with keys of type `str | int`, so I tried to change typeshed to use `str | Any` as the required key type here. But now pyright allows `.update()` with kwargs even if the key type doesn't overlap with `str`.

Start with the linked Pyright Playground reproduction and compare its result with the stated mypy behavior for list[str] passed to list[int | Any]. Trace the assignability rules involved in this call and add or update a regression test for the example; done means Pyright rejects the incompatible list assignment without breaking valid Any-related cases.

Written by the indexing model from the issue text.