feat: add removeMemberFromGroup and updateGroupMetadata to AccountViewModel

- Wire removeMember through AccountViewModel for UI access
- Add updateGroupMetadata to MlsGroupManager with Mutex protection

https://claude.ai/code/session_018gVkmmYgMFtBH7G31pCk9N

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

@@ -1480,8 +1480,10 @@ class AccountViewModel(
         val groupRelays =
             metadata
                 ?.relays
-                ?.mapNotNull { com.vitorpamplona.quartz.nip01Core.relay.normalizer.RelayUrlNormalizer.normalizeOrNull(it) }
+                ?.mapNotNull {
-                ?.toSet()
+                    com.vitorpamplona.quartz.nip01Core.relay.normalizer.RelayUrlNormalizer
+                        .normalizeOrNull(it)
+                }?.toSet()
         return if (!groupRelays.isNullOrEmpty()) groupRelays else account.outboxRelays.flow.value
     }
 

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/marmot/mls/group/MlsGroupManager.kt

@@ -27,6 +27,7 @@ import com.vitorpamplona.quartz.marmot.mls.messages.CommitResult
 import com.vitorpamplona.quartz.marmot.mls.messages.KeyPackageBundle
 import com.vitorpamplona.quartz.marmot.mls.schedule.KeySchedule
 import com.vitorpamplona.quartz.marmot.mls.schedule.SecretTree
+import com.vitorpamplona.quartz.marmot.mls.tree.Extension
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.utils.Log
 import kotlinx.coroutines.sync.Mutex
@@ -368,6 +369,23 @@ class MlsGroupManager(
             result
         }
 
+    /**
+     * Update group extensions (e.g., MIP-01 metadata) via a GroupContextExtensions proposal.
+     * Creates the proposal, commits it, and persists the new state.
+     */
+    suspend fun updateGroupExtensions(
+        nostrGroupId: HexKey,
+        extensions: List<Extension>,
+    ): CommitResult =
+        mutex.withLock {
+            val group = requireGroup(nostrGroupId)
+            retainEpochSecrets(nostrGroupId, group)
+            group.proposeGroupContextExtensions(extensions)
+            val result = group.commit()
+            persistGroup(nostrGroupId)
+            result
+        }
+
     /**
      * Leave a group (self-remove).
      * Returns the SelfRemove proposal bytes to publish, then removes