feat(desktop): Messages draggable divider + alignment polish + centered empty states

- **Draggable list pane**: the 280dp-fixed conversation list width is
  now user-adjustable via a draggable divider between the list and the
  chat pane. Width is clamped to 220-480dp and persisted across app
  restarts via DesktopPreferences.messagesListWidthDp. Cursor flips to
  the horizontal-resize arrow on hover.
- **ConversationCard alignment**: the unread indicator used to sit as
  an 8dp dot + 14dp spacer to the left of the avatar, which pushed
  every card ~14dp inward from the header row's 12dp padding. The
  avatar now starts flush with the header (aligned with the top-bar
  buttons); the unread state is drawn as a 10dp dot overlaid on the
  avatar's bottom-right corner (iMessage / Slack-style), with a
  surface-matched ring so it reads clearly against the avatar.
- **Drafts empty state**: was a flush-left Text pinned 16dp below the
  header; now uses the shared EmptyState composable so "No drafts
  yet" / description is vertically + horizontally centered in the
  available space, consistent with Notifications / Highlights / etc.

https://claude.ai/code/session_01NufduPfZvYQVYwLkbCjCUo

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/DesktopPreferences.kt

@@ -37,6 +37,7 @@ object DesktopPreferences {
     private const val KEY_LAST_SCREEN = "last_screen"
     private const val KEY_DECK_COLUMNS = "deck_columns"
     private const val KEY_LAYOUT_MODE = "layout_mode"
+    private const val KEY_MESSAGES_LIST_WIDTH = "messages_list_width_dp"
 
     var feedMode: FeedMode
         get() {
@@ -69,6 +70,13 @@ object DesktopPreferences {
             prefs.put(KEY_LAYOUT_MODE, value)
         }
 
+    /** Width (dp) of the conversation list pane in the Messages screen. */
+    var messagesListWidthDp: Float
+        get() = prefs.getFloat(KEY_MESSAGES_LIST_WIDTH, 280f)
+        set(value) {
+            prefs.putFloat(KEY_MESSAGES_LIST_WIDTH, value)
+        }
+
     private const val KEY_WORKSPACES = "workspaces"
 
     var workspaces: String

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/DraftsScreen.kt

@@ -53,6 +53,7 @@ import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
 import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
 import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
+import com.vitorpamplona.amethyst.commons.ui.components.EmptyState
 import com.vitorpamplona.amethyst.desktop.service.drafts.DesktopDraftStore
 import com.vitorpamplona.amethyst.desktop.service.drafts.DraftEntry
 import kotlinx.coroutines.launch
@@ -94,13 +95,10 @@ fun DraftsScreen(
             }
         }
 
-        Spacer(Modifier.height(16.dp))
-
         if (drafts.isEmpty()) {
-            Text(
-                "No drafts yet. Click \"New Draft\" to start writing.",
-                style = MaterialTheme.typography.bodyMedium,
-                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            EmptyState(
+                title = "No drafts yet",
+                description = "Click \"New Draft\" to start writing.",
             )
         } else {
             LazyColumn(

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/chats/ConversationListPane.kt

@@ -306,35 +306,39 @@ private fun ConversationCard(
                 .padding(horizontal = 12.dp, vertical = 10.dp),
         verticalAlignment = Alignment.CenterVertically,
     ) {
-        // Unread indicator
-        if (item.hasUnread) {
-            Box(
-                modifier =
-                    Modifier
-                        .size(8.dp)
-                        .clip(CircleShape)
-                        .background(MaterialTheme.colorScheme.primary),
-            )
-            Spacer(Modifier.width(6.dp))
-        } else {
-            Spacer(Modifier.width(14.dp))
-        }
-
-        // Avatar
+        // Avatar — starts flush with the header's 12dp padding. Unread state is
+        // signalled by a small primary-coloured dot overlaid on the avatar's
+        // bottom-right corner (Slack / iMessage-style), not an inline indent
+        // that would push the whole card to the right of the header label.
         val firstUser = item.users.firstOrNull()
-        if (firstUser != null) {
-            UserAvatar(
-                userHex = firstUser.pubkeyHex,
-                pictureUrl = firstUser.profilePicture(),
-                size = 40.dp,
-            )
-        } else if (item.isGroup) {
-            Icon(
-                MaterialSymbols.Group,
-                contentDescription = "Group",
-                modifier = Modifier.size(40.dp),
-                tint = MaterialTheme.colorScheme.onSurfaceVariant,
-            )
+        Box {
+            if (firstUser != null) {
+                UserAvatar(
+                    userHex = firstUser.pubkeyHex,
+                    pictureUrl = firstUser.profilePicture(),
+                    size = 40.dp,
+                )
+            } else if (item.isGroup) {
+                Icon(
+                    MaterialSymbols.Group,
+                    contentDescription = "Group",
+                    modifier = Modifier.size(40.dp),
+                    tint = MaterialTheme.colorScheme.onSurfaceVariant,
+                )
+            }
+            if (item.hasUnread) {
+                Box(
+                    modifier =
+                        Modifier
+                            .align(Alignment.BottomEnd)
+                            .size(10.dp)
+                            .clip(CircleShape)
+                            .background(MaterialTheme.colorScheme.surfaceContainer)
+                            .padding(1.5.dp)
+                            .clip(CircleShape)
+                            .background(MaterialTheme.colorScheme.primary),
+                )
+            }
         }
 
         Spacer(Modifier.width(10.dp))

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/chats/DesktopMessagesScreen.kt

@@ -21,6 +21,7 @@
 package com.vitorpamplona.amethyst.desktop.ui.chats
 
 import androidx.compose.foundation.background
+import androidx.compose.foundation.gestures.detectDragGestures
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxHeight
@@ -51,6 +52,9 @@ import androidx.compose.ui.input.key.isShiftPressed
 import androidx.compose.ui.input.key.key
 import androidx.compose.ui.input.key.onPreviewKeyEvent
 import androidx.compose.ui.input.key.type
+import androidx.compose.ui.input.pointer.PointerIcon
+import androidx.compose.ui.input.pointer.pointerHoverIcon
+import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.ui.unit.dp
 import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
 import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
@@ -63,6 +67,7 @@ import com.vitorpamplona.amethyst.desktop.model.DesktopIAccount
 import com.vitorpamplona.amethyst.desktop.network.DesktopRelayConnectionManager
 import com.vitorpamplona.quartz.nip17Dm.base.ChatroomKey
 import kotlinx.coroutines.CoroutineScope
+import java.awt.Cursor
 
 private val isMacOS = System.getProperty("os.name").lowercase().contains("mac")
 
@@ -273,6 +278,15 @@ private fun SplitMessagesContent(
     onShowRelayPicker: () -> Unit = {},
     keyHandler: Modifier,
 ) {
+    // Draggable split: the conversation list width is user-adjustable and
+    // persisted so it survives app restarts.
+    var listWidth by remember {
+        androidx.compose.runtime.mutableStateOf(
+            com.vitorpamplona.amethyst.desktop.DesktopPreferences.messagesListWidthDp.dp,
+        )
+    }
+    val density = androidx.compose.ui.platform.LocalDensity.current
+
     Row(modifier = Modifier.fillMaxSize().then(keyHandler)) {
         ConversationListPane(
             state = listState,
@@ -281,10 +295,17 @@ private fun SplitMessagesContent(
             onNewConversation = onShowNewDm,
             onShowRelayPicker = onShowRelayPicker,
             focusRequester = listFocusRequester,
-            modifier = Modifier.width(280.dp),
+            modifier = Modifier.width(listWidth),
         )
 
-        VerticalDivider(modifier = Modifier.fillMaxHeight())
+        MessagesDraggableDivider(
+            onDrag = { deltaPx ->
+                val deltaDp = with(density) { deltaPx.toDp() }
+                val next = (listWidth + deltaDp).coerceIn(220.dp, 480.dp)
+                listWidth = next
+                com.vitorpamplona.amethyst.desktop.DesktopPreferences.messagesListWidthDp = next.value
+            },
+        )
 
         Box(
             modifier =
@@ -357,3 +378,28 @@ private fun EmptyConversationState() {
         }
     }
 }
+
+/**
+ * Draggable vertical divider between the conversation list pane and the chat
+ * pane. 12dp wide hit area; cursor flips to the horizontal resize arrow on
+ * hover.
+ */
+@Composable
+private fun MessagesDraggableDivider(onDrag: (Float) -> Unit) {
+    Box(
+        modifier =
+            Modifier
+                .width(12.dp)
+                .fillMaxHeight()
+                .pointerHoverIcon(PointerIcon(Cursor(Cursor.E_RESIZE_CURSOR)))
+                .pointerInput(Unit) {
+                    detectDragGestures { change, dragAmount ->
+                        change.consume()
+                        onDrag(dragAmount.x)
+                    }
+                },
+        contentAlignment = Alignment.Center,
+    ) {
+        VerticalDivider(color = MaterialTheme.colorScheme.outlineVariant)
+    }
+}