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>

tests/HSchool.Protocol.Tests/ProtocolCodecTests.cs

@@ -246,7 +246,120 @@ public class ProtocolCodecTests
         Assert.Equal("f0.c0", read.People[0].Id);
         Assert.Equal("classroom-101", read.People[0].NodeId);
         Assert.Equal(PresenceState.Here, read.People[0].State);
+        Assert.Empty(read.People[0].TalkMemberIds);
+        Assert.Equal("", read.People[0].TalkTopicId);
         Assert.Equal(PresenceState.Walking, read.People[1].State);
+        Assert.Empty(read.People[1].TalkMemberIds);
+    }
+
+    [Fact]
+    public void Presence_PersonWithoutCircle_WritesEmptyMemberListAndEmptyTopic()
+    {
+        var message = new ServerPresenceMessage(
+            1,
+            [],
+            [new PresencePerson("f0.c0", "corridor-1", PresenceState.Here)]);
+        var buffer = new byte[ProtocolCodec.PresenceSize(message)];
+
+        var length = ProtocolCodec.WritePresence(buffer, message);
+
+        Assert.Equal((byte)MessageType.ServerPresence, buffer[0]);
+        Assert.Equal(1, BitConverter.ToInt32(buffer.AsSpan(1, 4)));
+        Assert.Equal((ushort)0, BitConverter.ToUInt16(buffer.AsSpan(5, 2)));
+        Assert.Equal((ushort)1, BitConverter.ToUInt16(buffer.AsSpan(7, 2)));
+
+        var offset = 9;
+        offset = AssertWireString(buffer, offset, "f0.c0");
+        offset = AssertWireString(buffer, offset, "corridor-1");
+        Assert.Equal(PresenceState.Here, buffer[offset]);
+        offset += 1;
+        Assert.Equal(0, buffer[offset]);
+        offset += 1;
+        offset = AssertWireString(buffer, offset, "");
+        Assert.Equal(length, offset);
+        Assert.Equal(length, ProtocolCodec.PresenceSize(message));
+
+        var read = ProtocolCodec.ReadPresence(buffer.AsSpan(0, length));
+        Assert.Empty(read.People[0].TalkMemberIds);
+        Assert.Equal("", read.People[0].TalkTopicId);
+        Assert.Equal(message.People[0].Id, read.People[0].Id);
+        Assert.Equal(message.People[0].NodeId, read.People[0].NodeId);
+        Assert.Equal(message.People[0].State, read.People[0].State);
+    }
+
+    [Fact]
+    public void Presence_PersonWithCircle_RoundTripsMemberIdsAndTopic()
+    {
+        var members = new[] { "f0.c0", "f0.c1" };
+        var message = new ServerPresenceMessage(
+            1,
+            [new PresenceNode("corridor-1", 2)],
+            [new PresencePerson("f0.c0", "corridor-1", PresenceState.Here, members, "TopicSport")]);
+        var buffer = new byte[ProtocolCodec.PresenceSize(message)];
+
+        var length = ProtocolCodec.WritePresence(buffer, message);
+
+        Assert.Equal((byte)MessageType.ServerPresence, buffer[0]);
+        Assert.Equal(1, BitConverter.ToInt32(buffer.AsSpan(1, 4)));
+        Assert.Equal((ushort)1, BitConverter.ToUInt16(buffer.AsSpan(5, 2)));
+
+        var offset = 7;
+        offset = AssertWireString(buffer, offset, "corridor-1");
+        Assert.Equal((ushort)2, BitConverter.ToUInt16(buffer.AsSpan(offset, 2)));
+        offset += 2;
+        Assert.Equal(0, buffer[offset]);
+        offset += 1;
+        Assert.Equal((ushort)1, BitConverter.ToUInt16(buffer.AsSpan(offset, 2)));
+        offset += 2;
+        offset = AssertWireString(buffer, offset, "f0.c0");
+        offset = AssertWireString(buffer, offset, "corridor-1");
+        Assert.Equal(PresenceState.Here, buffer[offset]);
+        offset += 1;
+        Assert.Equal(2, buffer[offset]);
+        offset += 1;
+        offset = AssertWireString(buffer, offset, "f0.c0");
+        offset = AssertWireString(buffer, offset, "f0.c1");
+        offset = AssertWireString(buffer, offset, "TopicSport");
+        Assert.Equal(length, offset);
+        Assert.Equal(length, ProtocolCodec.PresenceSize(message));
+
+        var read = ProtocolCodec.ReadPresence(buffer.AsSpan(0, length));
+        Assert.Equal(["f0.c0", "f0.c1"], read.People[0].TalkMemberIds);
+        Assert.Equal("TopicSport", read.People[0].TalkTopicId);
+        Assert.Equal(message.SchoolId, read.SchoolId);
+        Assert.Equal(message.People[0].Id, read.People[0].Id);
+    }
+
+    [Fact]
+    public void Presence_DoesNotContainPersonDisplayName()
+    {
+        var message = new ServerPresenceMessage(
+            1,
+            [],
+            [new PresencePerson(
+                "f0.c0",
+                "corridor-1",
+                PresenceState.Here,
+                ["f0.c0", "f0.c1"],
+                "TopicSport")]);
+        var buffer = new byte[ProtocolCodec.PresenceSize(message)];
+
+        ProtocolCodec.WritePresence(buffer, message);
+        var text = System.Text.Encoding.UTF8.GetString(buffer);
+
+        Assert.DoesNotContain("Мария", text);
+        Assert.DoesNotContain("Иванова", text);
+        Assert.DoesNotContain("Маша", text);
+        Assert.Contains("f0.c0", text);
+        Assert.Contains("TopicSport", text);
+    }
+
+    private static int AssertWireString(byte[] buffer, int offset, string expected)
+    {
+        var bytes = System.Text.Encoding.UTF8.GetBytes(expected);
+        Assert.Equal((ushort)bytes.Length, BitConverter.ToUInt16(buffer.AsSpan(offset, 2)));
+        Assert.Equal(bytes, buffer.AsSpan(offset + 2, bytes.Length).ToArray());
+        return offset + 2 + bytes.Length;
     }
 
     [Fact]