feat: add Marmot group info screen, member list, and leave group

Based on MIP spec review, add missing UI screens:

MarmotManager additions (commons):
- memberPubkeys(): extract Nostr pubkeys from MLS ratchet tree
  leaf nodes via Credential.Basic identity
- memberCount(): get group member count
- groupEpoch(): expose current MLS epoch
- GroupMemberInfo data class for leaf index + pubkey pairs

Account & AccountViewModel:
- leaveMarmotGroup(): publish SelfRemove proposal and clean up
- marmotGroupMembers(): expose member list to UI

MarmotGroupInfoScreen (new):
- Group metadata header (name, ID, epoch, member count)
- Member list with leaf indices, clickable to view profiles
- "Leave Group" with confirmation dialog
- "Add Member" access from group info

Navigation:
- Route.MarmotGroupInfo added and wired into nav graph
- Chat screen title now clickable to navigate to group info

https://claude.ai/code/session_0194SxKfAU61PY92eqP4cCXM

amethyst/src/main/java/com/vitorpamplona/amethyst/model/Account.kt

@@ -1804,6 +1804,21 @@ class Account(
         manager.createGroup(nostrGroupId)
     }
 
+    /**
+     * Leave a Marmot MLS group.
+     * Publishes the SelfRemove proposal and removes local state.
+     */
+    suspend fun leaveMarmotGroup(
+        nostrGroupId: HexKey,
+        groupRelays: Set<NormalizedRelayUrl>,
+    ) {
+        val manager = marmotManager ?: return
+        if (!isWriteable()) return
+
+        val outbound = manager.leaveGroup(nostrGroupId)
+        client.publish(outbound.signedEvent, groupRelays)
+    }
+
     suspend fun createStatus(newStatus: String) = sendMyPublicAndPrivateOutbox(UserStatusAction.create(newStatus, signer))
 
     suspend fun publishCallSignaling(wrap: EphemeralGiftWrapEvent) {

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/AppNavigation.kt

@@ -72,6 +72,7 @@ import com.vitorpamplona.amethyst.ui.screen.loggedIn.bookmarkgroups.membershipMa
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.bookmarkgroups.membershipManagement.PostBookmarkListManagementScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.bookmarkgroups.old.OldBookmarkListScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup.MarmotGroupChatScreen
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup.MarmotGroupInfoScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup.MarmotGroupListScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.privateDM.ChatroomByAuthorScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.privateDM.ChatroomScreen
@@ -286,6 +287,7 @@ fun BuildNavigation(
 
         composableFromEnd<Route.MarmotGroupList> { MarmotGroupListScreen(accountViewModel, nav) }
         composableFromEndArgs<Route.MarmotGroupChat> { MarmotGroupChatScreen(it.nostrGroupId, accountViewModel, nav) }
+        composableFromEndArgs<Route.MarmotGroupInfo> { MarmotGroupInfoScreen(it.nostrGroupId, accountViewModel, nav) }
 
         composableFromEndArgs<Route.PublicChatChannel> {
             PublicChatChannelScreen(it.id, it.draftId, it.replyTo, accountViewModel, nav)

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/routes/Routes.kt

@@ -269,6 +269,10 @@ sealed class Route {
         val nostrGroupId: String,
     ) : Route()
 
+    @Serializable data class MarmotGroupInfo(
+        val nostrGroupId: String,
+    ) : Route()
+
     @Serializable data class NewGroupDM(
         val message: String? = null,
         val attachment: String? = null,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/AccountViewModel.kt

@@ -1464,6 +1464,13 @@ class AccountViewModel(
         account.publishMarmotKeyPackage()
     }
 
+    suspend fun leaveMarmotGroup(nostrGroupId: String) {
+        val relays = account.outboxRelays.flow.value
+        account.leaveMarmotGroup(nostrGroupId, relays)
+    }
+
+    fun marmotGroupMembers(nostrGroupId: String): List<com.vitorpamplona.amethyst.commons.marmot.GroupMemberInfo> = account.marmotManager?.memberPubkeys(nostrGroupId) ?: emptyList()
+
     override fun onCleared() {
         Log.d("AccountViewModel", "onCleared")
         callController?.cleanup()

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/marmotGroup/MarmotGroupChatScreen.kt

@@ -20,6 +20,7 @@
  */
 package com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup
 
+import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.consumeWindowInsets
 import androidx.compose.foundation.layout.padding
@@ -41,6 +42,7 @@ import androidx.compose.ui.Modifier
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.vitorpamplona.amethyst.ui.layouts.DisappearingScaffold
 import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.routes.Route
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 
@@ -72,7 +74,12 @@ fun MarmotGroupChatScreen(
                     }
                 },
                 title = {
-                    Column {
+                    Column(
+                        modifier =
+                            Modifier.clickable {
+                                nav.nav(Route.MarmotGroupInfo(nostrGroupId))
+                            },
+                    ) {
                         Text(displayName ?: "Marmot Group")
                         if (memberCount > 0) {
                             Text(

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/marmotGroup/MarmotGroupInfoScreen.kt

@@ -0,0 +1,297 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup
+
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.ArrowBack
+import androidx.compose.material.icons.automirrored.filled.ExitToApp
+import androidx.compose.material.icons.filled.GroupAdd
+import androidx.compose.material.icons.filled.Person
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.HorizontalDivider
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.material3.TopAppBar
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.commons.marmot.GroupMemberInfo
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.routes.Route
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun MarmotGroupInfoScreen(
+    nostrGroupId: HexKey,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    val chatroom =
+        remember(nostrGroupId) {
+            accountViewModel.account.marmotGroupList.getOrCreateGroup(nostrGroupId)
+        }
+    val displayName by chatroom.displayName.collectAsStateWithLifecycle()
+    var members by remember { mutableStateOf(emptyList<GroupMemberInfo>()) }
+    var showLeaveDialog by remember { mutableStateOf(false) }
+    var showAddMemberDialog by remember { mutableStateOf(false) }
+    val scope = rememberCoroutineScope()
+    val myPubkey = accountViewModel.account.signer.pubKey
+
+    LaunchedEffect(nostrGroupId) {
+        members = accountViewModel.marmotGroupMembers(nostrGroupId)
+        chatroom.memberCount.value = members.size
+    }
+
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                navigationIcon = {
+                    IconButton(onClick = { nav.popBack() }) {
+                        Icon(
+                            imageVector = Icons.AutoMirrored.Filled.ArrowBack,
+                            contentDescription = "Back",
+                        )
+                    }
+                },
+                title = { Text("Group Info") },
+                actions = {
+                    IconButton(onClick = { showAddMemberDialog = true }) {
+                        Icon(
+                            imageVector = Icons.Default.GroupAdd,
+                            contentDescription = "Add Member",
+                        )
+                    }
+                },
+            )
+        },
+    ) { padding ->
+        LazyColumn(
+            modifier =
+                Modifier
+                    .fillMaxSize()
+                    .padding(padding),
+        ) {
+            // Group header section
+            item {
+                Column(
+                    modifier =
+                        Modifier
+                            .fillMaxWidth()
+                            .padding(16.dp),
+                ) {
+                    Text(
+                        text = displayName ?: "Group ${nostrGroupId.take(8)}...",
+                        style = MaterialTheme.typography.headlineSmall,
+                        fontWeight = FontWeight.Bold,
+                    )
+                    Text(
+                        text = "${members.size} members",
+                        style = MaterialTheme.typography.bodyMedium,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                        modifier = Modifier.padding(top = 4.dp),
+                    )
+                    Text(
+                        text = "Group ID: ${nostrGroupId.take(16)}...",
+                        style = MaterialTheme.typography.bodySmall,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                        modifier = Modifier.padding(top = 2.dp),
+                    )
+                    val epoch = accountViewModel.account.marmotManager?.groupEpoch(nostrGroupId)
+                    if (epoch != null) {
+                        Text(
+                            text = "Epoch: $epoch",
+                            style = MaterialTheme.typography.bodySmall,
+                            color = MaterialTheme.colorScheme.onSurfaceVariant,
+                            modifier = Modifier.padding(top = 2.dp),
+                        )
+                    }
+                }
+                HorizontalDivider()
+            }
+
+            // Members section header
+            item {
+                Text(
+                    text = "Members",
+                    style = MaterialTheme.typography.titleMedium,
+                    fontWeight = FontWeight.Bold,
+                    modifier = Modifier.padding(horizontal = 16.dp, vertical = 12.dp),
+                )
+            }
+
+            // Member list
+            items(members, key = { it.leafIndex }) { member ->
+                MemberRow(
+                    member = member,
+                    isMe = member.pubkey == myPubkey,
+                    onClick = {
+                        nav.nav(Route.Profile(member.pubkey))
+                    },
+                )
+                HorizontalDivider()
+            }
+
+            // Leave group section
+            item {
+                HorizontalDivider(modifier = Modifier.padding(top = 8.dp))
+                Row(
+                    modifier =
+                        Modifier
+                            .fillMaxWidth()
+                            .clickable { showLeaveDialog = true }
+                            .padding(horizontal = 16.dp, vertical = 16.dp),
+                    verticalAlignment = Alignment.CenterVertically,
+                    horizontalArrangement = Arrangement.spacedBy(12.dp),
+                ) {
+                    Icon(
+                        imageVector = Icons.AutoMirrored.Filled.ExitToApp,
+                        contentDescription = "Leave Group",
+                        tint = MaterialTheme.colorScheme.error,
+                    )
+                    Text(
+                        text = "Leave Group",
+                        style = MaterialTheme.typography.bodyLarge,
+                        color = MaterialTheme.colorScheme.error,
+                    )
+                }
+            }
+        }
+    }
+
+    if (showLeaveDialog) {
+        LeaveGroupDialog(
+            groupName = displayName ?: "this group",
+            onConfirm = {
+                showLeaveDialog = false
+                scope.launch(Dispatchers.IO) {
+                    accountViewModel.leaveMarmotGroup(nostrGroupId)
+                }
+                nav.nav(Route.MarmotGroupList)
+            },
+            onDismiss = { showLeaveDialog = false },
+        )
+    }
+
+    if (showAddMemberDialog) {
+        AddMemberDialog(
+            nostrGroupId = nostrGroupId,
+            accountViewModel = accountViewModel,
+            onDismiss = { showAddMemberDialog = false },
+        )
+    }
+}
+
+@Composable
+fun MemberRow(
+    member: GroupMemberInfo,
+    isMe: Boolean,
+    onClick: () -> Unit,
+) {
+    Row(
+        modifier =
+            Modifier
+                .fillMaxWidth()
+                .clickable(onClick = onClick)
+                .padding(horizontal = 16.dp, vertical = 10.dp),
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(12.dp),
+    ) {
+        Icon(
+            imageVector = Icons.Default.Person,
+            contentDescription = null,
+            modifier = Modifier.size(36.dp),
+            tint = MaterialTheme.colorScheme.onSurfaceVariant,
+        )
+        Column(modifier = Modifier.weight(1f)) {
+            Text(
+                text =
+                    if (isMe) {
+                        "${member.pubkey.take(16)}... (you)"
+                    } else {
+                        "${member.pubkey.take(16)}..."
+                    },
+                style = MaterialTheme.typography.bodyMedium,
+                maxLines = 1,
+                overflow = TextOverflow.Ellipsis,
+                fontWeight = if (isMe) FontWeight.Bold else FontWeight.Normal,
+            )
+            Text(
+                text = "Leaf #${member.leafIndex}",
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+    }
+}
+
+@Composable
+fun LeaveGroupDialog(
+    groupName: String,
+    onConfirm: () -> Unit,
+    onDismiss: () -> Unit,
+) {
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text("Leave Group") },
+        text = {
+            Text("Are you sure you want to leave \"$groupName\"? You will no longer receive messages from this group.")
+        },
+        confirmButton = {
+            TextButton(onClick = onConfirm) {
+                Text("Leave", color = MaterialTheme.colorScheme.error)
+            }
+        },
+        dismissButton = {
+            TextButton(onClick = onDismiss) {
+                Text("Cancel")
+            }
+        },
+    )
+}

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/marmot/MarmotManager.kt

@@ -35,6 +35,7 @@ import com.vitorpamplona.quartz.marmot.mip02Welcome.WelcomeEvent
 import com.vitorpamplona.quartz.marmot.mip03GroupMessages.GroupEvent
 import com.vitorpamplona.quartz.marmot.mls.group.MlsGroupManager
 import com.vitorpamplona.quartz.marmot.mls.group.MlsGroupStateStore
+import com.vitorpamplona.quartz.marmot.mls.tree.Credential
 import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.nip01Core.core.hexToByteArray
@@ -254,4 +255,44 @@ class MarmotManager(
      * Get all active group IDs.
      */
     fun activeGroupIds(): Set<HexKey> = groupManager.activeGroupIds()
+
+    // --- Group Info ---
+
+    /**
+     * Get the member count for a group.
+     */
+    fun memberCount(nostrGroupId: HexKey): Int = groupManager.getGroup(nostrGroupId)?.memberCount ?: 0
+
+    /**
+     * Get the member list for a group.
+     * Returns leaf index and Nostr pubkey (extracted from BasicCredential) for each member.
+     */
+    fun memberPubkeys(nostrGroupId: HexKey): List<GroupMemberInfo> {
+        val group = groupManager.getGroup(nostrGroupId) ?: return emptyList()
+        return group.members().mapNotNull { (leafIndex, leafNode) ->
+            val pubkey =
+                when (val cred = leafNode.credential) {
+                    is Credential.Basic -> cred.identity.toHexKey()
+                    else -> null
+                }
+            if (pubkey != null) {
+                GroupMemberInfo(leafIndex = leafIndex, pubkey = pubkey)
+            } else {
+                null
+            }
+        }
+    }
+
+    /**
+     * Get the current epoch for a group.
+     */
+    fun groupEpoch(nostrGroupId: HexKey): Long? = groupManager.getGroup(nostrGroupId)?.epoch
 }
+
+/**
+ * Information about a member in a Marmot MLS group.
+ */
+data class GroupMemberInfo(
+    val leafIndex: Int,
+    val pubkey: HexKey,
+)