Auto-scroll nest chat to newest message when at bottom

Both NestFullScreen and NestLobbyScreen render the kind-1311
transcript with LazyColumn(reverseLayout = true). When a new message
is prepended, LazyColumn preserves visual position by shifting
firstVisibleItemIndex from 0 to 1, leaving the new message just below
the viewport — the user has to scroll down to see it.

If the user is at (or one item from) the bottom when a new message
arrives, scroll back to item 0 so the newest message is visible. If
they are reading older history, leave them where they are.

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/nests/room/chat/NestChatPanel.kt

@@ -35,6 +35,7 @@ import androidx.compose.foundation.lazy.rememberLazyListState
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.remember
@@ -100,6 +101,19 @@ internal fun ColumnScope.NestChatPanel(
 
     val listState = rememberLazyListState()
 
+    // Auto-stick to the newest message. With reverseLayout=true, item 0
+    // is the bottom of the viewport (newest). When a new message is
+    // prepended, LazyColumn preserves visual position by shifting
+    // firstVisibleItemIndex from 0 → 1, leaving the new message just
+    // below the viewport. If the user was at (or near) the bottom,
+    // scroll back to 0 so the new message becomes visible. If they're
+    // reading older history, leave them where they are.
+    LaunchedEffect(messages.firstOrNull()?.idHex) {
+        if (listState.firstVisibleItemIndex <= 1) {
+            listState.animateScrollToItem(0)
+        }
+    }
+
     Column(modifier = modifier.fillMaxWidth()) {
         Box(
             modifier =

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/nests/room/lobby/NestLobbyScreen.kt

@@ -164,6 +164,19 @@ private fun NestLobbyContent(
     val listState = rememberLazyListState()
     val scope = rememberCoroutineScope()
 
+    // Auto-stick to the newest message. With reverseLayout=true, item 0
+    // is the bottom of the viewport (newest). When a new message is
+    // prepended, LazyColumn preserves visual position by shifting
+    // firstVisibleItemIndex from 0 → 1, leaving the new message just
+    // below the viewport. If the user was at (or near) the bottom,
+    // scroll back to 0 so the new message becomes visible. If they're
+    // reading older history, leave them where they are.
+    LaunchedEffect(messages.firstOrNull()?.idHex) {
+        if (listState.firstVisibleItemIndex <= 1) {
+            listState.animateScrollToItem(0)
+        }
+    }
+
     Scaffold(
         contentWindowInsets = WindowInsets(0),
         topBar = {