Fix for Voyager TabNavigator not disposing of nested navigators

FirstTab.kt

object FirstTab : Tab {
    override var navigator: Navigator? = null
    override val options: TabOptions
        @Composable
        get() = TODO("Not yet implemented")

    @Composable
    override fun Content() {
        Navigator(FirstTabFirstScreen()) {
            LaunchedEffect(it) {
                navigator = it
            }
            FadeTransition(it)
        }
    }
}

FirstTabFirstScreen.kt

class FirstTabFirstScreen : Screen {

    @Composable
    override fun Content(
    ) {
        // Content
    }
}

SampleTabScreen.kt

class SampleTabsScreen : Screen {
    private val tabs = listOf<Tab>()

    @Composable
    override fun Content() {
        TabNavigator(
            tab = tabs.first(),
            tabDisposable = { navigator ->
                TabDisposable(navigator, tabs)
            },
        ) {
            CurrentTab()
        }
    }
}

Tab.kt

import androidx.compose.runtime.Composable
import androidx.compose.ui.graphics.painter.Painter
import cafe.adriel.voyager.core.screen.Screen
import cafe.adriel.voyager.navigator.Navigator

@Composable
public fun CurrentTab() {
    val tabNavigator = LocalTabNavigator.current
    val currentTab = tabNavigator.current

    tabNavigator.saveableState("currentTab") {
        currentTab.Content()
    }
}

public data class TabOptions(
    val index: UShort,
    val title: String,
    val icon: Painter? = null
)

public interface Tab : Screen {
    public var navigator: Navigator?

    public val options: TabOptions
        @Composable get
}

TabNavigator.kt

import androidx.compose.runtime.Composable
import androidx.compose.runtime.CompositionLocalProvider
import androidx.compose.runtime.ProvidableCompositionLocal
import androidx.compose.runtime.remember
import androidx.compose.runtime.staticCompositionLocalOf
import cafe.adriel.voyager.core.annotation.InternalVoyagerApi
import cafe.adriel.voyager.core.lifecycle.DisposableEffectIgnoringConfiguration
import cafe.adriel.voyager.navigator.Navigator
import cafe.adriel.voyager.navigator.NavigatorDisposeBehavior
import cafe.adriel.voyager.navigator.compositionUniqueId

public typealias TabNavigatorContent = @Composable (tabNavigator: TabNavigator) -> Unit

public val LocalTabNavigator: ProvidableCompositionLocal<TabNavigator> =
    staticCompositionLocalOf { error("TabNavigator not initialized") }

@OptIn(InternalVoyagerApi::class)
@Composable
public fun TabNavigator(
    tab: Tab,
    disposeNestedNavigators: Boolean = false,
    tabDisposable: (@Composable (TabNavigator) -> Unit)? = null,
    key: String = compositionUniqueId(),
    content: TabNavigatorContent = { CurrentTab() }
) {
    Navigator(
        screen = tab,
        disposeBehavior = NavigatorDisposeBehavior(
            disposeNestedNavigators = disposeNestedNavigators,
            disposeSteps = false
        ),
        onBackPressed = null,
        key = key
    ) { navigator ->
        val tabNavigator = remember(navigator) {
            TabNavigator(navigator)
        }

        tabDisposable?.invoke(tabNavigator)

        CompositionLocalProvider(LocalTabNavigator provides tabNavigator) {
            content(tabNavigator)
        }
    }
}

@OptIn(InternalVoyagerApi::class)
@Composable
public fun TabDisposable(navigator: TabNavigator, tabs: List<Tab>) {
    DisposableEffectIgnoringConfiguration(Unit) {
        onDispose {
            tabs.forEach { tab ->
                navigator.navigator.dispose(tab)
                tab.navigator?.let { tabNavigator ->
                    tabNavigator.items.forEach {
                        tabNavigator.dispose(it)
                    }
                }
            }
        }
    }
}

public class TabNavigator internal constructor(
    internal val navigator: Navigator
) {

    public var current: Tab
        get() = navigator.lastItem as Tab
        set(tab) = navigator.replaceAll(tab)

    @Composable
    public fun saveableState(
        key: String,
        tab: Tab = current,
        content: @Composable () -> Unit
    ) {
        navigator.saveableState(key, tab, content = content)
    }
}