fix(ui): keep previous search results while reloading

Keep showing the last results while a new search generation loads,
and guard list access: the paging snapshot can shrink mid-layout,
which threw and crashed on an empty result set.

app/src/main/java/com/example/research/ui/main/SearchResultsPane.kt

@@ -8,6 +8,7 @@ import androidx.compose.foundation.layout.ime
 import androidx.compose.foundation.text.input.TextFieldState
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.SideEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
@@ -50,6 +51,7 @@ internal fun SearchResultsPane(
     var restoredScrollPosition by remember { mutableStateOf(false) }
     var pendingScrollToTop by remember { mutableStateOf(false) }
     var sawRefreshForPendingScroll by remember { mutableStateOf(false) }
+    var staleEntries by remember { mutableStateOf(emptyList<IndexEntry>()) }
     val imeBottomPadding = with(LocalDensity.current) {
         WindowInsets.ime.getBottom(this).toDp()
     }
@@ -72,8 +74,27 @@ internal fun SearchResultsPane(
                 restoredScrollPosition = true
                 pendingScrollToTop = query.isNotBlank()
                 sawRefreshForPendingScroll = false
+                if (query.isBlank()) {
+                    staleEntries = emptyList()
                 }
             }
+    }
+
+    val loaded = ArrayList<IndexEntry>(results.itemCount)
+    for (index in 0 until results.itemCount) {
+        val entry = results.peek(index)
+        if (entry != null) {
+            loaded.add(entry)
+        }
+    }
+    SideEffect {
+        if (results.loadState.refresh is LoadState.NotLoading && loaded.isNotEmpty()) {
+            staleEntries = loaded
+        }
+    }
+    val pendingReload = results.itemCount == 0 &&
+        results.loadState.refresh is LoadState.Loading
+    val shownStale = if (pendingReload && searchState.text.isNotBlank()) staleEntries else emptyList()
 
     LaunchedEffect(results.loadState.refresh, pendingScrollToTop) {
         if (pendingScrollToTop && results.loadState.refresh is LoadState.Loading) {
@@ -125,6 +146,7 @@ internal fun SearchResultsPane(
             listState = listState,
             showDictionaryName = showDictionaryName,
             contentPadding = PaddingValues(bottom = imeBottomPadding),
+            staleEntries = shownStale,
         )
     }
 }

app/src/main/java/com/example/research/ui/main/components/SearchResultsList.kt

@@ -30,8 +30,11 @@ fun SearchResultsList(
     modifier: Modifier = Modifier,
     listState: LazyListState = rememberLazyListState(),
     showDictionaryName: Boolean = true,
-    contentPadding: PaddingValues = PaddingValues()
+    contentPadding: PaddingValues = PaddingValues(),
+    staleEntries: List<IndexEntry> = emptyList(),
 ) {
+    val showStale = staleEntries.isNotEmpty() && results.itemCount == 0
+    val rowCount = if (showStale) staleEntries.size else results.itemCount
     LazyColumn(
         modifier = modifier
             .testTag("search_results")
@@ -41,11 +44,18 @@ fun SearchResultsList(
         verticalArrangement = Arrangement.spacedBy(4.dp)
     ) {
         items(
-            count = results.itemCount,
+            count = rowCount,
-            key = results.itemKey { "${it.dictionaryPath}:${it.offset.value}:${it.word}" },
+            key = { index ->
-            contentType = results.itemContentType { "search_result" }
+                val entry = if (showStale) staleEntries.getOrNull(index)
+                else if (index in 0 until results.itemCount) results.peek(index) else null
+                entry?.let { "${it.dictionaryPath}:${it.offset.value}:${it.word}" }
+                    ?: "search_result_$index"
+            },
+            contentType = { "search_result" }
         ) { index ->
-            results[index]?.let { entry ->
+            val entry = if (showStale) staleEntries.getOrNull(index)
+            else if (index in 0 until results.itemCount) results.peek(index) else null
+            if (entry != null) {
                 Box(
                     modifier = Modifier.animateItem(
                         fadeInSpec = if (index < 8) tween(150) else null,