Should check that generated stubs have type annotations

When creating type stubs with stubgen and pyright, members which aren't explicitly annotated generally don't get a type annontation.

For example, when generating stubs with stubgen -p shiny, the resulting _shinyenv.pyi file had the following:

from _typeshed import Incomplete

is_pyodide: Incomplete

With pyright --create-stubs shiny, the result is similar:

is_pyodide = ...

The same thing happens when class instance members are defined within the init method. For example, suppose a class has something like this:

class Test:
    def __init__(x: int):
        self.x = x
``

When `stubgen` generates the stub, it loses the type for `x`:

```py
from _typeshed import Incomplete

class Test:
    x: Incomplete
    def __init__(x: int) -> None: ...

When pyright generates the stub, it loses information about x completely. The result is:

class Test:
    def __init__() -> None:
        ...

This was partially addressed in 57c39b771b32322c8c833a47339bb644f67a2261.

I think the best way to go about checking for this is to use stubgen in CI and search for any instances of Incomplete.

Start with the stubgen and pyright entry points described in the issue, generating stubs for the shiny package and inspecting the resulting .pyi files. Check how CI currently runs and how generated output can be searched for Incomplete or missing member types. Done means CI reliably detects the annotation loss described for module members and instance members.