debug(marmot): log removeMarmotGroupMember + syncMetadataTo transitions

The bug report: after tapping Remove on the Marmot Group Info screen,
the target npub stays in the member list, and the only log line is
the round-tripped kind:445 hitting the "Duplicate" branch in
GroupEventHandler.add. The author-side path (Account.removeMarmotGroupMember
→ MarmotManager.removeMember → syncMetadataTo → publish) has no logging,
so there's no way to tell which step broke — the MLS tree mutation,
the local member-list push to chatroom.members, or the UI recomposition.

Mirror the addMarmotGroupMember logging style on removeMarmotGroupMember
(entry, no-op guards, built commit id, publish) so we can see whether
the author path even runs end-to-end, and have syncMetadataTo log the
group id and the previous→new member count so the StateFlow update
becomes observable. No behavior change.

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

@@ -2313,12 +2313,30 @@ class Account(
         targetLeafIndex: Int,
         groupRelays: Set<NormalizedRelayUrl>,
     ) {
-        val manager = marmotManager ?: return
-        if (!isWriteable()) return
+        Log.d("MarmotDbg") {
+            "removeMarmotGroupMember: group=${nostrGroupId.take(8)}… targetLeafIndex=$targetLeafIndex " +
+                "groupRelays=${groupRelays.size}"
+        }
+        val manager =
+            marmotManager ?: run {
+                Log.w("MarmotDbg") { "removeMarmotGroupMember: marmotManager is NULL — no-op" }
+                return
+            }
+        if (!isWriteable()) {
+            Log.w("MarmotDbg") { "removeMarmotGroupMember: account is not writeable — no-op" }
+            return
+        }
 
         val outbound = manager.removeMember(nostrGroupId, targetLeafIndex)
+        Log.d("MarmotDbg") {
+            "removeMarmotGroupMember: built commit kind=${outbound.signedEvent.kind} id=${outbound.signedEvent.id.take(8)}…"
+        }
         val chatroom = marmotGroupList.getOrCreateGroup(nostrGroupId)
         manager.syncMetadataTo(nostrGroupId, chatroom)
+        Log.d("MarmotDbg") {
+            "removeMarmotGroupMember: publishing commit id=${outbound.signedEvent.id.take(8)}… " +
+                "to ${groupRelays.size} relay(s): ${groupRelays.map { it.url }}"
+        }
         client.publish(outbound.signedEvent, groupRelays)
     }