False positive unreachable with unrelated types in match-case statement

Nobody has claimed this yet.

**Describe the bug**
When type in a class pattern of a `case` branch is unrelated to the type of the scrutinee, pyright reports the branch as unreachable. That’s incorrect, because a common subclass of both types can exist.

**Code or Screenshots**
This code prints `reached` in runtime, but pyright reports the branch as unreachable and infers the type of `t` as `Never` instead of correct “subclass of `Foo` and `Bar`” as [mypy does](https://mypy-play.net/?mypy=latest&python=3.12&gist=4f94c718861b7f6a9182381a3d95b24c).

```python
class Foo:
pass

class Bar:
pass

class Baz(Foo, Bar):
pass

def check(x: Foo) -> None:
match x:
case Bar() as t:
print('reached', t)

check(Baz())
```

**VS Code extension or command-line**
I’m running pyright in Neovim, but this also reproduces [on playground](https://pyright-play.net/?pythonVersion=3.13&code=MYGwhgzhAEBiD28BcAoa7oAdIRS0O0AQmAE6oZY54FTFgBeAFAvADT2kCUFG2UeACYBTAGbRgAC2HAA1kwAeSOIi7QAtAD5oAOXgA7Yb3QBbMABcp0JWkoZgkYZyZrI0c8buVMpAJb7zJgByUmEwKWFBII5zLhppOSYSZi44oA).

Start with the linked pyright playground reproduction and trace the match-case reachability and type-narrowing diagnostics it produces. Confirm the fix when the branch is no longer reported as unreachable and t is inferred as a possible subclass of both Foo and Bar, while the example still runs unchanged.

Written by the indexing model from the issue text.