fix(navigation): keep Home composed while article is open

Article was an AnimatedContent target: opening it disposed Home, and returning from it recreated the whole results list in a single frame. The article screen now renders as a full-screen AnimatedVisibility overlay above Home, which stays composed for the whole article session.

app/src/main/java/com/example/research/ui/navigation/AppNavigation.kt

@@ -2,16 +2,22 @@ package com.example.research.ui.navigation
 
 import androidx.activity.compose.BackHandler
 import androidx.compose.animation.AnimatedContent
+import androidx.compose.animation.AnimatedVisibility
 import androidx.compose.animation.fadeIn
 import androidx.compose.animation.fadeOut
 import androidx.compose.animation.slideInHorizontally
 import androidx.compose.animation.slideOutHorizontally
 import androidx.compose.animation.togetherWith
 import androidx.compose.animation.core.tween
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Surface
 import androidx.compose.material3.adaptive.ExperimentalMaterial3AdaptiveApi
 import androidx.compose.material3.adaptive.currentWindowAdaptiveInfoV2
 import androidx.compose.runtime.*
 import androidx.compose.runtime.saveable.*
+import androidx.compose.ui.Modifier
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.window.core.layout.WindowSizeClass.Companion.WIDTH_DP_MEDIUM_LOWER_BOUND
 import com.example.research.feature.search.SearchAction
@@ -101,10 +107,11 @@ fun AppNavigation(
 
     val effectiveScreen = when {
         currentScreen == Screen.About -> Screen.About
-        currentScreen == Screen.Article && articleState == null -> if (shouldShowSettings) Screen.Settings else Screen.Home
         shouldShowSettings -> Screen.Settings
-        else -> currentScreen
+        currentScreen == Screen.Settings -> Screen.Settings
+        else -> Screen.Home
     }
+    Box {
     AnimatedContent(
         targetState = effectiveScreen,
         transitionSpec = {
@@ -150,7 +157,27 @@ fun AppNavigation(
                 onNavigateToAbout = { screenStack.add(Screen.About) }
             )
         }
-        Screen.Article -> {
+        Screen.About -> {
+            AboutScreen(
+                onNavigateBack = {
+                    if (screenStack.size > 1) screenStack.removeAt(screenStack.lastIndex)
+                }
+            )
+        }
+        Screen.Article -> {}
+        }
+    }
+
+    AnimatedVisibility(
+        visible = currentScreen == Screen.Article && articleState != null,
+        enter = fadeIn(tween(180)) + slideInHorizontally(tween(180)) { it / 3 },
+        exit = fadeOut(tween(180)) + slideOutHorizontally(tween(180)) { it / 3 },
+        label = "articleOverlay",
+    ) {
+        Surface(
+            modifier = Modifier.fillMaxSize(),
+            color = MaterialTheme.colorScheme.surface
+        ) {
             ArticleRoute(
                 searchViewModel = searchViewModel,
                 onNavigateBack = {
@@ -162,13 +189,6 @@ fun AppNavigation(
                 }
             )
         }
-        Screen.About -> {
+    }
-            AboutScreen(
-                onNavigateBack = {
-                    if (screenStack.size > 1) screenStack.removeAt(screenStack.lastIndex)
-                }
-            )
-        }
-        }
     }
 }