feat(nests): wrap room screen in Scaffold; title + overflow → TopAppBar

The room name and the MoreVert overflow lived inline at the top of
the metadata Column, so they scrolled with the rest. Hoist them into
a Material 3 TopAppBar inside a Scaffold, matching every other major
screen in the app.

NestTopAppBar — new private composable:
  - Title is `event.room()`, single-line ellipsis.
  - Actions: Box wrapping the MoreVert IconButton + DropdownMenu
    (Share for everyone, Edit gated on `isHost`).
  - containerColor = Transparent so the themed background painted by
    NestThemedScope's Surface (and any optional `bg` image) shows
    through cleanly without a double-paint.

NestFullScreen body now:
  Scaffold(
    containerColor = Color.Transparent,
    topBar = { NestTopAppBar(...) },
  ) { padding ->
    Column(fillMaxSize.padding(padding)) {
      Column(weight(1, false), verticalScroll, hpad+top pad) {
        // summary, listener count, participants grid, host actions
        // sheet, hand-raise queue, connection row, talk row, action
        // row, reaction picker, host-leave confirm dialog
      }
      NestChatPanel(weight(1, true), hpad+bottom pad)
    }
  }

Side effects:
  - Drops the manual windowInsetsPadding(safeDrawing) — Scaffold's
    contentWindowInsets handles that and the TopAppBar's own
    windowInsets handles the top edge.
  - The EditNestSheet conditional moves to NestThemedScope's body
    (after the Scaffold). It's a ModalBottomSheet, so position in
    the tree doesn't change layout, but adjacency to the Scaffold
    keeps the sheet/dialog boundary obvious.

https://claude.ai/code/session_01RDpuki4t8StSg1CZcXnV5b

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

@@ -28,12 +28,9 @@ import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
-import androidx.compose.foundation.layout.WindowInsets
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
-import androidx.compose.foundation.layout.safeDrawing
-import androidx.compose.foundation.layout.windowInsetsPadding
 import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.verticalScroll
 import androidx.compose.material3.AlertDialog
@@ -41,11 +38,18 @@ import androidx.compose.material3.AssistChip
 import androidx.compose.material3.AssistChipDefaults
 import androidx.compose.material3.Button
 import androidx.compose.material3.ButtonDefaults
+import androidx.compose.material3.DropdownMenu
+import androidx.compose.material3.DropdownMenuItem
+import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.FilledTonalIconToggleButton
+import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
+import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
+import androidx.compose.material3.TopAppBar
+import androidx.compose.material3.TopAppBarDefaults
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
@@ -55,7 +59,9 @@ import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
 import androidx.core.content.ContextCompat
 import com.vitorpamplona.amethyst.R
@@ -98,87 +104,58 @@ internal fun NestFullScreen(
 ) {
     val roomTheme = androidx.compose.runtime.remember(event) { RoomTheme.from(event) }
     NestThemedScope(theme = roomTheme, accountViewModel = accountViewModel) {
-        // Outer column owns the safeDrawing inset; the top metadata
-        // section and the chat panel are weighted siblings.
-        //
-        // The top section uses `weight(1f, fill = false)` so it never
-        // exceeds half the screen and scrolls internally if it would.
-        // The chat uses `weight(1f, fill = true)` so it always takes
-        // its full allocation — the user explicitly wanted chat to
-        // dominate the screen rather than ride a fixed-height box at
-        // the bottom of the metadata scroll.
-        Column(
-            modifier =
-                Modifier
-                    .fillMaxSize()
-                    .windowInsetsPadding(WindowInsets.safeDrawing),
-        ) {
         var showEditSheet by rememberSaveable { mutableStateOf(false) }
         var showHostMenu by rememberSaveable { mutableStateOf(false) }
         var showHostLeaveConfirm by rememberSaveable { mutableStateOf(false) }
         val isHost = accountViewModel.account.signer.pubKey == event.pubKey
         val leaveScope = rememberCoroutineScope()
+        val topBarContext = LocalContext.current
 
+        // Scaffold owns safeDrawing insets via its `contentWindowInsets`
+        // default, so we don't manage them manually anymore. The
+        // container is transparent because NestThemedScope's outer
+        // Surface already paints the themed background (and overlays
+        // the optional `bg` image on top of it); painting again here
+        // would double up.
+        Scaffold(
+            modifier = Modifier.fillMaxSize(),
+            containerColor = Color.Transparent,
+            topBar = {
+                NestTopAppBar(
+                    title = event.room().orEmpty(),
+                    isHost = isHost,
+                    showHostMenu = showHostMenu,
+                    onMenuOpen = { showHostMenu = true },
+                    onMenuDismiss = { showHostMenu = false },
+                    onShare = {
+                        showHostMenu = false
+                        shareRoomNaddr(topBarContext, event)
+                    },
+                    onEdit = {
+                        showHostMenu = false
+                        showEditSheet = true
+                    },
+                )
+            },
+        ) { padding ->
+            // Inner column is just the two weighted siblings — top
+            // metadata (scrolls internally if overflow) and the chat
+            // panel (takes the rest). Title and overflow menu live in
+            // the TopAppBar above.
+            Column(
+                modifier =
+                    Modifier
+                        .fillMaxSize()
+                        .padding(padding),
+            ) {
                 Column(
                     modifier =
                         Modifier
                             .weight(1f, fill = false)
                             .verticalScroll(rememberScrollState())
                             .padding(horizontal = 16.dp)
-                        .padding(top = 16.dp),
+                            .padding(top = 8.dp),
                 ) {
-                Row(
-                    modifier = Modifier.fillMaxWidth(),
-                    horizontalArrangement = Arrangement.SpaceBetween,
-                    verticalAlignment = Alignment.Top,
-                ) {
-                    event.room()?.let {
-                        Text(
-                            text = it,
-                            style = MaterialTheme.typography.headlineSmall,
-                            modifier = Modifier.weight(1f),
-                        )
-                    }
-                    // Overflow menu — visible to everyone (Share); host-only
-                    // rows (Edit) are gated inside.
-                    Box {
-                        androidx.compose.material3.IconButton(onClick = { showHostMenu = true }) {
-                            Icon(
-                                symbol = MaterialSymbols.MoreVert,
-                                contentDescription = stringRes(R.string.nest_overflow_menu),
-                            )
-                        }
-                        val context = androidx.compose.ui.platform.LocalContext.current
-                        androidx.compose.material3.DropdownMenu(
-                            expanded = showHostMenu,
-                            onDismissRequest = { showHostMenu = false },
-                        ) {
-                            androidx.compose.material3.DropdownMenuItem(
-                                text = { Text(stringRes(R.string.nest_share_action)) },
-                                onClick = {
-                                    showHostMenu = false
-                                    shareRoomNaddr(context, event)
-                                },
-                            )
-                            if (isHost) {
-                                androidx.compose.material3.DropdownMenuItem(
-                                    text = { Text(stringRes(R.string.nest_edit_title)) },
-                                    onClick = {
-                                        showHostMenu = false
-                                        showEditSheet = true
-                                    },
-                                )
-                            }
-                        }
-                    }
-                }
-                if (showEditSheet) {
-                    EditNestSheet(
-                        accountViewModel = accountViewModel,
-                        event = event,
-                        onDismiss = { showEditSheet = false },
-                    )
-                }
                     event.summary()?.let {
                         Text(
                             text = it,
@@ -355,6 +332,79 @@ internal fun NestFullScreen(
                 )
             }
         }
+
+        // EditNestSheet renders as a ModalBottomSheet — placement in
+        // the tree doesn't affect layout, but keeping it adjacent to
+        // the Scaffold makes the dialog/sheet boundary obvious.
+        if (showEditSheet) {
+            EditNestSheet(
+                accountViewModel = accountViewModel,
+                event = event,
+                onDismiss = { showEditSheet = false },
+            )
+        }
+    }
+}
+
+/**
+ * TopAppBar for the room screen — hosts the room name and the
+ * overflow menu (Share for everyone, Edit for the host). The menu
+ * state lives at the screen level so the EditNestSheet can be
+ * triggered from here and rendered alongside the Scaffold.
+ *
+ * Container color is transparent so the themed background painted
+ * by [NestThemedScope]'s Surface (and any optional `bg` image) shows
+ * through cleanly.
+ */
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+private fun NestTopAppBar(
+    title: String,
+    isHost: Boolean,
+    showHostMenu: Boolean,
+    onMenuOpen: () -> Unit,
+    onMenuDismiss: () -> Unit,
+    onShare: () -> Unit,
+    onEdit: () -> Unit,
+) {
+    TopAppBar(
+        title = {
+            Text(
+                text = title,
+                maxLines = 1,
+                overflow = TextOverflow.Ellipsis,
+            )
+        },
+        actions = {
+            Box {
+                IconButton(onClick = onMenuOpen) {
+                    Icon(
+                        symbol = MaterialSymbols.MoreVert,
+                        contentDescription = stringRes(R.string.nest_overflow_menu),
+                    )
+                }
+                DropdownMenu(
+                    expanded = showHostMenu,
+                    onDismissRequest = onMenuDismiss,
+                ) {
+                    DropdownMenuItem(
+                        text = { Text(stringRes(R.string.nest_share_action)) },
+                        onClick = onShare,
+                    )
+                    if (isHost) {
+                        DropdownMenuItem(
+                            text = { Text(stringRes(R.string.nest_edit_title)) },
+                            onClick = onEdit,
+                        )
+                    }
+                }
+            }
+        },
+        colors =
+            TopAppBarDefaults.topAppBarColors(
+                containerColor = Color.Transparent,
+            ),
+    )
 }
 
 @Composable