Revisit Wear Splash Screen and Cold Boot

Revisit of https://github.com/home-assistant/android/issues/1883

Wear 4+ has an automatic splash screen, which is hard to beat.

But if still desired, then the guidance is to avoid separate activities.

See https://developer.android.com/training/wearables/apps/splash-screen#update-starting-activity

```
class MainActivity : ComponentActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
// Handle the splash screen transition.
installSplashScreen()

super.onCreate(savedInstanceState)
setContent {
WearApp("Wear OS app")
}
}
}
```

Review the related issue 1883 and the linked Wear OS splash-screen guidance first. The payload identifies MainActivity and installSplashScreen() as the relevant entry point; determine whether Wear 4+ automatic behavior is sufficient or whether the startup flow should be revisited. Done means the cold-boot splash behavior and the decision to change or retain it are verified.

Written by the indexing model from the issue text.