Compile error when exposing a `Char` property in idl

### Describe the bug

[From this documentation](https://learn.microsoft.com/en-us/uwp/midl-3/intro#types), it should be able to expose a `Char` type from the idl, but doing this will cause a compile error:
```
static_assert(impl::has_category_v, "T must be WinRT type.");
```

I [originally posted in cppwinrt repo](https://github.com/microsoft/cppwinrt/issues/1566), but seems like it's winui code gen issue.

### Why is this important?

Aligning to the documentation.

### Steps to reproduce the bug

Use this idl
```cpp
[default_interface]
runtimeclass MainPage : Windows.UI.Xaml.Controls.Page
{
MainPage();
Char MyProperty;
}
```

### Actual behavior

Build error

### Expected behavior

_No response_

### Screenshots

_No response_

### NuGet package version

1.8.260317003

### Windows version

Windows 11 (24H2): Build 26100

### Additional context

_No response_

Reproduce the compile error with the provided MIDL 3 IDL containing a Char property and the stated WinUI package version. Start by tracing the generated C++ around the reported has_category_v assertion; done means the IDL compiles and the Char property is exposed without that error.

Written by the indexing model from the issue text.