Incorrect unused variable diagnosis in loops

With this code:

```bzl
def foo():
    found = False
    for i in range(10):
        if found:
            break
        if i == 5:
            found = True
    return ""
```

You see this warning about `found` never being accessed:

<img width="488" height="144" alt="Image" src="https://github.com/user-attachments/assets/0f0499a4-2ae3-4ec0-8b14-2dede9371915" />