REDI-96: repository MockEngine test + Compose robot UI test + serialization fix

NetworkCharacterRepositoryTest swaps a Ktor MockEngine into HttpClientFactory and
covers success mapping (incl. request URL/page-param construction), 404 ->
NOT_FOUND, 500 -> SERVER_ERROR, and malformed body -> SERIALIZATION. That last
case exposed a real bug: Ktor wraps the kotlinx SerializationException in its own
ContentConvertException, so safeCall mapped it to UNKNOWN; safeCall now scans the
cause chain and maps it to SERIALIZATION. Adds an instrumented Compose UI test
(CharacterListScreen) using the chaining CharacterListRobot: rendered items,
empty/error states, and tap -> Action.

feature/characters/presentation-compose/src/androidTest/kotlin/com/example/architecture/feature/characters/presentation/compose/CharacterListRobot.kt

@@ -0,0 +1,81 @@
+package com.example.architecture.feature.characters.presentation.compose
+
+import android.content.Context
+import androidx.compose.ui.test.assertIsDisplayed
+import androidx.compose.ui.test.junit4.ComposeContentTestRule
+import androidx.compose.ui.test.onNodeWithText
+import androidx.compose.ui.test.performClick
+import com.example.architecture.core.design.system.theme.AppTheme
+import com.example.architecture.feature.characters.presentation.CharacterListAction
+import com.example.architecture.feature.characters.presentation.CharacterListState
+import org.junit.Assert.assertTrue
+
+/**
+ * Robot for [CharacterListScreen] UI tests. Each method returns `this` so calls read as a fluent
+ * scenario (`robot.setContent(state).assertCharacterShown(...).clickCharacter(...)`). The robot owns
+ * the interaction vocabulary; the test owns the assertions' intent — keeping tests readable and
+ * resilient to UI structure changes. See android-testing.
+ */
+class CharacterListRobot(
+    private val composeRule: ComposeContentTestRule,
+    private val context: Context,
+) {
+    private val recordedActions = mutableListOf<CharacterListAction>()
+
+    fun setContent(state: CharacterListState): CharacterListRobot {
+        composeRule.setContent {
+            AppTheme {
+                CharacterListScreen(
+                    state = state,
+                    onAction = { recordedActions += it },
+                    onOpenAbout = {},
+                    onOpenViewsList = {},
+                    onOpenErrorDemo = {},
+                )
+            }
+        }
+        return this
+    }
+
+    fun assertCharacterShown(name: String): CharacterListRobot {
+        composeRule.onNodeWithText(name).assertIsDisplayed()
+        return this
+    }
+
+    fun assertEmptyStateShown(): CharacterListRobot {
+        composeRule.onNodeWithText(context.getString(R.string.characters_empty)).assertIsDisplayed()
+        return this
+    }
+
+    fun assertErrorShown(message: String): CharacterListRobot {
+        composeRule.onNodeWithText(message).assertIsDisplayed()
+        return this
+    }
+
+    fun assertRetryShown(): CharacterListRobot {
+        composeRule.onNodeWithText(retryLabel).assertIsDisplayed()
+        return this
+    }
+
+    fun clickCharacter(name: String): CharacterListRobot {
+        composeRule.onNodeWithText(name).performClick()
+        return this
+    }
+
+    fun clickRetry(): CharacterListRobot {
+        composeRule.onNodeWithText(retryLabel).performClick()
+        return this
+    }
+
+    fun assertActionRecorded(action: CharacterListAction): CharacterListRobot {
+        assertTrue(
+            "Expected $action to be recorded, but got $recordedActions",
+            recordedActions.contains(action),
+        )
+        return this
+    }
+
+    // The retry label lives in the design-system module; reference its R directly (non-transitive R).
+    private val retryLabel: String
+        get() = context.getString(com.example.architecture.core.design.system.R.string.designsystem_retry)
+}

feature/characters/presentation-compose/src/androidTest/kotlin/com/example/architecture/feature/characters/presentation/compose/CharacterListScreenTest.kt

@@ -0,0 +1,77 @@
+package com.example.architecture.feature.characters.presentation.compose
+
+import android.content.Context
+import androidx.compose.ui.test.junit4.createComposeRule
+import androidx.test.core.app.ApplicationProvider
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.example.architecture.core.presentation.UiText
+import com.example.architecture.feature.characters.domain.model.CharacterStatus
+import com.example.architecture.feature.characters.presentation.CharacterListAction
+import com.example.architecture.feature.characters.presentation.CharacterListState
+import com.example.architecture.feature.characters.presentation.model.CharacterUi
+import kotlinx.collections.immutable.persistentListOf
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+
+/**
+ * Instrumented Compose UI test for [CharacterListScreen] using [CharacterListRobot]. Runs on a
+ * device/emulator (`connectedDebugAndroidTest`); CI assembles it. Asserts rendered items, the
+ * empty + error states, and that user gestures fire the right MVI [CharacterListAction]s.
+ */
+@RunWith(AndroidJUnit4::class)
+class CharacterListScreenTest {
+
+    @get:Rule
+    val composeRule = createComposeRule()
+
+    private val context: Context = ApplicationProvider.getApplicationContext()
+
+    private fun robot() = CharacterListRobot(composeRule, context)
+
+    private val loadedState = CharacterListState(
+        characters = persistentListOf(
+            CharacterUi(1, "Rick Sanchez", "Human", "", CharacterStatus.ALIVE),
+            CharacterUi(2, "Morty Smith", "Human", "", CharacterStatus.ALIVE),
+        ),
+    )
+
+    @Test
+    fun rendersCharacterItems() {
+        robot()
+            .setContent(loadedState)
+            .assertCharacterShown("Rick Sanchez")
+            .assertCharacterShown("Morty Smith")
+    }
+
+    @Test
+    fun showsEmptyState() {
+        robot()
+            .setContent(CharacterListState())
+            .assertEmptyStateShown()
+    }
+
+    @Test
+    fun showsErrorStateWithRetry() {
+        robot()
+            .setContent(CharacterListState(error = UiText.DynamicString("Boom")))
+            .assertErrorShown("Boom")
+            .assertRetryShown()
+    }
+
+    @Test
+    fun tappingAnItemFiresOnCharacterClick() {
+        robot()
+            .setContent(loadedState)
+            .clickCharacter("Rick Sanchez")
+            .assertActionRecorded(CharacterListAction.OnCharacterClick(1))
+    }
+
+    @Test
+    fun tappingRetryFiresOnRetry() {
+        robot()
+            .setContent(CharacterListState(error = UiText.DynamicString("Boom")))
+            .clickRetry()
+            .assertActionRecorded(CharacterListAction.OnRetry)
+    }
+}