`reportUnknownVariableType` sometimes not reported

**Describe the bug**

`reportUnknownVariableType` is sometimes not reported.

In the `foo` function below, `r` is revealed (in the mouse-over) as `dict[Unknown, Unknown]`, but the unknown type is not reported.

**Code or Screenshots**

```python
from typing import TypedDict

class TypedDictA(TypedDict):
a: int

class TypedDictB(TypedDict):
r: dict[str, TypedDictA]

def foo() -> TypedDictB:
# no reportUnknownVariableType triggered anywhere here
r = {}
r["r_key"] = {
"a": "a",
}
return {
"r": r,
}

def goo() -> TypedDictA:
p = {}
return p # correctly triggers reportUnknownVariableType
```

pyright playground link:

https://pyright-play.net/?strict=true&code=GYJw9gtgBALgngBwJYDsDmUkQWEMoAqiApgCYAiSAxjAFD1UA2AhgM6uEkXUwCCAFEQRlKNAJQAuWlBlRmEzCjoMW7TsO40AQoK6iYk6bJALSPANqsYIADTqRPXgF16tUsWBRgYMPzFQAWgA%2Be00YLSlZKABiKBQwKBBiHDwAVRQAa3iAdxQANWYQJGYAI0ZiIWJYIrQ0YiTSORQ4bIALeqr2pKMZECgAXigAbwBfHsTzACIQAH0M4jhJpwHh8ajJ5kmFDcmbcbGopJgAVxAUVaj1kC3Evaix%2BndPNB8-QJDKsN5I2QQV0fGR1O5z%2BMSgVFwSRojDg1SQtXqHCSKRg6SyYFyBSKpXKlVoQA

Start by running the linked Pyright playground example with strict mode and compare diagnostics in foo and goo. Trace how the empty dictionary assignment is handled alongside reportUnknownVariableType. Done means the reproduced case reports the unknown variable type consistently and has a regression test covering it.

Written by the indexing model from the issue text.