Bump protocol to v9 and carry talk-circle ids on the presence frame.

Names stay off the wire; a person not in a circle writes an empty member list and topic.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/HSchool.Protocol/ProtocolCodec.cs

@@ -202,6 +202,14 @@ public static class ProtocolCodec
         foreach (var person in message.People)
         {
             size += StringSize(person.Id) + StringSize(person.NodeId) + sizeof(byte);
+            var members = person.TalkMemberIds ?? [];
+            size += sizeof(byte);
+            foreach (var memberId in members)
+            {
+                size += StringSize(memberId);
+            }
+
+            size += StringSize(person.TalkTopicId ?? "");
         }
 
         return size;
@@ -242,9 +250,22 @@ public static class ProtocolCodec
         writer.WriteUInt16((ushort)message.People.Count);
         foreach (var person in message.People)
         {
+            var members = person.TalkMemberIds ?? [];
+            if (members.Count > byte.MaxValue)
+            {
+                throw new ProtocolException($"Presence person {person.Id} has {members.Count} talk members; u8 count cannot hold it.");
+            }
+
             writer.WriteString(person.Id);
             writer.WriteString(person.NodeId);
             writer.WriteByte(person.State);
+            writer.WriteByte((byte)members.Count);
+            foreach (var memberId in members)
+            {
+                writer.WriteString(memberId);
+            }
+
+            writer.WriteString(person.TalkTopicId ?? "");
         }
 
         return writer.Position;
@@ -403,7 +424,18 @@ public static class ProtocolCodec
         var people = new PresencePerson[personCount];
         for (var i = 0; i < personCount; i++)
         {
-            people[i] = new PresencePerson(reader.ReadString(), reader.ReadString(), reader.ReadByte());
+            var id = reader.ReadString();
+            var nodeId = reader.ReadString();
+            var state = reader.ReadByte();
+            var memberCount = reader.ReadByte();
+            var members = new string[memberCount];
+            for (var member = 0; member < memberCount; member++)
+            {
+                members[member] = reader.ReadString();
+            }
+
+            var topicId = reader.ReadString();
+            people[i] = new PresencePerson(id, nodeId, state, members, topicId);
         }
 
         return new ServerPresenceMessage(schoolId, nodes, people);