Errors when building SampleListDetailPaneScaffold.kt

# Issue

The ["Build a list-detail layout" page](https://developer.android.com/develop/ui/compose/layouts/adaptive/list-detail) and sample has some issues. Specifically:

+ The "Build a list-detail app" page might benefit from more code sample snippets per step.
+ The page and code should also clearly mark what are user-provided values (e.g. MyItem) vs. what are platform-provided. For example, it took a bit of scanning in the GitHub code file to find what `shortStrings` was.
+ Error when building/analyzing this code:

```
Argument type mismatch: actual type is
'androidx.compose.material3.adaptive.navigation.ThreePaneScaffoldNavigator',
but
'androidx.compose.material3.adaptive.navigation.ThreePaneScaffoldNavigator'
was expected.
```

# Environment

+ macOS
+ Android Studio Narwhal

Start with SampleListDetailPaneScaffold.kt and the linked “Build a list-detail layout” page, then build or analyze the sample in Android Studio to reproduce the navigator type mismatch. Compare the sample with the documented steps and identify the user-provided versus platform-provided values. Done means the sample builds and the page includes clearer snippets and explanations.

Written by the indexing model from the issue text.