Update wire protocol to version 7 and enhance presence management features

- Bumped the wire protocol version to 7, reflecting significant changes in the communication structure.
- Introduced a new presence message type for real-time occupancy updates, including node activity and individual presence states.
- Updated the API to include a directory endpoint for fetching short id→name mappings, improving client-side name resolution.
- Revised the map snapshot structure to be static, with people and current lessons now handled through the presence stream.
- Enhanced client-side handling of presence updates, including UI adjustments to display live occupancy and activity.
- Updated documentation to reflect the new protocol features and changes in presence management.
- Added tests to validate the new presence functionalities and ensure robust handling of real-time data.

src/HSchool.Server/Net/GameSocketHandler.cs

@@ -153,6 +153,10 @@ internal sealed class GameSocketHandler(
                     commands.Enqueue(new GameCommand.SetSpeed(client.PlayerId, setSpeed.SpeedIndex));
                     break;
 
+                case MessageType.ClientSkipEmpty:
+                    commands.Enqueue(new GameCommand.SkipEmpty(client.PlayerId));
+                    break;
+
                 default:
                     logger.LogDebug(
                         "Ignoring unexpected frame 0x{MessageType:X2} from client {PlayerId}.",