REDI-90: character detail screen (type-safe nav args + MVI)

Add a CharacterDetail MVI stack (State/Action/Event/ViewModel + CharacterDetailUi)
to the UI-agnostic :feature:characters:presentation. The detail ViewModel reads the
typed characterId from SavedStateHandle (populated by the type-safe CharacterDetailRoute),
so the module keeps zero navigation/Compose deps.

Add CharacterDetailScreen (Root/Screen, image header, attribute rows, loading/error)
and CharacterDetailRoute to :presentation-compose; refactor charactersGraph to drive
list->detail via NavController and expose About / Views entries as callbacks. Extract
shared CharacterStatus label/colour helpers; add an overflow menu to the list app bar.

Add material-icons-core to the compose bundle for the app-bar icons.

feature/characters/presentation/src/main/kotlin/com/example/architecture/feature/characters/presentation/CharacterDetailAction.kt

@@ -0,0 +1,6 @@
+package com.example.architecture.feature.characters.presentation
+
+sealed interface CharacterDetailAction {
+    data object OnRetry : CharacterDetailAction
+    data object OnBackClick : CharacterDetailAction
+}

feature/characters/presentation/src/main/kotlin/com/example/architecture/feature/characters/presentation/CharacterDetailEvent.kt

@@ -0,0 +1,6 @@
+package com.example.architecture.feature.characters.presentation
+
+sealed interface CharacterDetailEvent {
+    /** One-time effect: the user asked to leave; the renderer pops the back stack. */
+    data object NavigateBack : CharacterDetailEvent
+}

feature/characters/presentation/src/main/kotlin/com/example/architecture/feature/characters/presentation/CharacterDetailState.kt

@@ -0,0 +1,14 @@
+package com.example.architecture.feature.characters.presentation
+
+import com.example.architecture.core.presentation.UiText
+import com.example.architecture.feature.characters.presentation.model.CharacterDetailUi
+
+/**
+ * UI state for the character detail screen. Like [CharacterListState] this is Compose-free: all
+ * fields are stable types, so no `@Stable` (and therefore no Compose dependency) is needed.
+ */
+data class CharacterDetailState(
+    val details: CharacterDetailUi? = null,
+    val isLoading: Boolean = false,
+    val error: UiText? = null,
+)

feature/characters/presentation/src/main/kotlin/com/example/architecture/feature/characters/presentation/CharacterDetailViewModel.kt

@@ -0,0 +1,73 @@
+package com.example.architecture.feature.characters.presentation
+
+import androidx.lifecycle.SavedStateHandle
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import com.example.architecture.core.domain.onFailure
+import com.example.architecture.core.domain.onSuccess
+import com.example.architecture.core.presentation.toUiText
+import com.example.architecture.feature.characters.domain.CharacterRepository
+import com.example.architecture.feature.characters.presentation.model.toCharacterDetailUi
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.receiveAsFlow
+import kotlinx.coroutines.flow.update
+import kotlinx.coroutines.launch
+
+/**
+ * UI-agnostic MVI ViewModel for the character detail screen.
+ *
+ * Type-safe navigation writes the route's typed `characterId` into [SavedStateHandle] under its
+ * field name. Reading that raw key — instead of `savedStateHandle.toRoute<CharacterDetailRoute>()` —
+ * is deliberate: it keeps this module free of any navigation/Compose dependency (the route type
+ * lives in the renderer). The renderer is what reads the route via `toRoute()`.
+ */
+class CharacterDetailViewModel(
+    savedStateHandle: SavedStateHandle,
+    private val characterRepository: CharacterRepository,
+) : ViewModel() {
+
+    private val characterId: Int = checkNotNull(savedStateHandle.get<Int>(KEY_CHARACTER_ID)) {
+        "CharacterDetailRoute.characterId missing from SavedStateHandle"
+    }
+
+    private val _state = MutableStateFlow(CharacterDetailState())
+    val state = _state.asStateFlow()
+
+    private val _events = Channel<CharacterDetailEvent>()
+    val events = _events.receiveAsFlow()
+
+    init {
+        loadDetails()
+    }
+
+    fun onAction(action: CharacterDetailAction) {
+        when (action) {
+            CharacterDetailAction.OnRetry -> loadDetails()
+            CharacterDetailAction.OnBackClick -> viewModelScope.launch {
+                _events.send(CharacterDetailEvent.NavigateBack)
+            }
+        }
+    }
+
+    private fun loadDetails() {
+        // Clear previous details too: a (re)load must never leave stale content beside a fresh error.
+        _state.update { it.copy(isLoading = true, error = null, details = null) }
+        viewModelScope.launch {
+            characterRepository.getCharacterDetails(characterId)
+                .onSuccess { details ->
+                    _state.update {
+                        it.copy(details = details.toCharacterDetailUi(), isLoading = false, error = null)
+                    }
+                }
+                .onFailure { failure ->
+                    _state.update { it.copy(isLoading = false, error = failure.toUiText()) }
+                }
+        }
+    }
+
+    private companion object {
+        const val KEY_CHARACTER_ID = "characterId"
+    }
+}

feature/characters/presentation/src/main/kotlin/com/example/architecture/feature/characters/presentation/di/CharactersPresentationModule.kt

@@ -1,10 +1,12 @@
 package com.example.architecture.feature.characters.presentation.di
 
+import com.example.architecture.feature.characters.presentation.CharacterDetailViewModel
 import com.example.architecture.feature.characters.presentation.CharacterListViewModel
 import org.koin.core.module.dsl.viewModelOf
 import org.koin.dsl.module
 
-/** Presentation DI for the characters feature. Lives with the (UI-agnostic) ViewModel it provides. */
+/** Presentation DI for the characters feature. Lives with the (UI-agnostic) ViewModels it provides. */
 val charactersPresentationModule = module {
     viewModelOf(::CharacterListViewModel)
+    viewModelOf(::CharacterDetailViewModel)
 }

feature/characters/presentation/src/main/kotlin/com/example/architecture/feature/characters/presentation/model/CharacterDetailUi.kt

@@ -0,0 +1,36 @@
+package com.example.architecture.feature.characters.presentation.model
+
+import com.example.architecture.feature.characters.domain.model.CharacterDetails
+import com.example.architecture.feature.characters.domain.model.CharacterStatus
+
+/**
+ * Presentation model for the character detail screen. Blank free-text API fields (notably `type`)
+ * are pre-formatted to an em dash here so the renderer stays dumb.
+ */
+data class CharacterDetailUi(
+    val id: Int,
+    val name: String,
+    val status: CharacterStatus,
+    val species: String,
+    val type: String,
+    val gender: String,
+    val origin: String,
+    val location: String,
+    val imageUrl: String,
+    val episodeCount: Int,
+)
+
+fun CharacterDetails.toCharacterDetailUi(): CharacterDetailUi = CharacterDetailUi(
+    id = id,
+    name = name,
+    status = status,
+    species = species.ifBlank { DASH },
+    type = type.ifBlank { DASH },
+    gender = gender.ifBlank { DASH },
+    origin = origin.ifBlank { DASH },
+    location = location.ifBlank { DASH },
+    imageUrl = imageUrl,
+    episodeCount = episodeCount,
+)
+
+private const val DASH = "—"