feat(article): adaptive compact top bar

Top-align the title row in compact layouts, align the back button
with the first title line using the shared back button, make the
title start padding depend on whether the back button is shown,
and drop the spacing constant the old arrow buttons used.

app/src/main/java/com/example/research/ui/article/ArticleScreen.kt

@@ -2,33 +2,59 @@ package com.example.research.ui.article
 
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.interaction.MutableInteractionSource
-import androidx.compose.foundation.layout.*
-import androidx.compose.foundation.text.selection.SelectionContainer
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.offset
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.windowInsetsPadding
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.itemsIndexed
 import androidx.compose.foundation.lazy.rememberLazyListState
-import androidx.compose.material3.*
-import androidx.compose.runtime.*
+import androidx.compose.foundation.text.selection.SelectionContainer
+import androidx.compose.material3.Button
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.key
+import androidx.compose.runtime.mutableIntStateOf
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberUpdatedState
 import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.compose.runtime.snapshotFlow
+import androidx.compose.runtime.withFrameNanos
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.luminance
 import androidx.compose.ui.layout.onSizeChanged
+import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.platform.testTag
-import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.semantics.testTagsAsResourceId
-import androidx.compose.ui.unit.dp
 import androidx.compose.ui.text.AnnotatedString
-import androidx.compose.ui.text.TextStyle
 import androidx.compose.ui.text.style.LineHeightStyle
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.IntSize
+import androidx.compose.ui.unit.dp
 import com.example.research.R
+import com.example.research.common.ui.AppBackButton
 import com.example.research.common.ui.theme.dictionaryTitleLarge
-import com.example.research.ui.theme.Spacing
 import com.example.research.ui.theme.AppWindowInsets
+import com.example.research.ui.theme.Spacing
 
 private const val MERGED_BLOCK_MAX_CHARS = 1500
 private const val MERGED_BLOCK_MAX_ITEMS = 12
@@ -263,7 +289,14 @@ fun ArticleTitleBar(
         null -> ""
     }
 
-    val backIcon = painterResource(R.drawable.ic_arrow_back)
+    val backButtonOffset = if (compact) {
+        val titleLineHeight = with(LocalDensity.current) {
+            MaterialTheme.typography.dictionaryTitleLarge.lineHeight.toDp()
+        }
+        Modifier.offset(y = (titleLineHeight - 48.dp) / 2)
+    } else {
+        Modifier
+    }
 
     Surface(
         color = MaterialTheme.colorScheme.surface,
@@ -282,22 +315,15 @@ fun ArticleTitleBar(
                             .height(Spacing.topBarHeight)
                     }
                 ),
-            verticalAlignment = Alignment.CenterVertically
+            verticalAlignment = if (compact) Alignment.Top else Alignment.CenterVertically
         ) {
             if (showBackButton) {
-                Box(
+                AppBackButton(
+                    onClick = onNavigateBack,
                     modifier = Modifier
-                        .padding(start = Spacing.iconStart)
-                        .size(24.dp)
-                        .clickable(onClick = onNavigateBack),
-                    contentAlignment = Alignment.Center
-                ) {
-                    Icon(
-                        painter = backIcon,
-                        contentDescription = stringResource(R.string.action_back),
-                        modifier = Modifier.size(24.dp)
-                    )
-                }
+                        .padding(start = 10.dp)
+                        .then(backButtonOffset)
+                )
             }
 
             key(selectionReset) {
@@ -309,7 +335,7 @@ fun ArticleTitleBar(
                         maxLines = 1,
                         overflow = TextOverflow.Ellipsis,
                         modifier = Modifier
-                            .padding(start = if (showBackButton) Spacing.searchTextStart - Spacing.iconStart - 24.dp else 16.dp)
+                            .padding(start = if (showBackButton) 0.dp else 16.dp)
                             .testTag("article_title")
                             .semantics { testTagsAsResourceId = true }
                     )

app/src/main/java/com/example/research/ui/theme/Spacing.kt

@@ -6,7 +6,6 @@ object Spacing {
     // Semantic spacing constants for specific UI elements
     val topBarPadding = 8.dp
     val topBarHeight = 56.dp
-    val iconStart = 32.dp
     val searchTextStart = 68.dp
     val listItemVertical = 8.dp