Add native DRO (Danganronpa Online) server support

Allows AO2-Client to connect directly to DRO servers without a proxy:
- Detect DRO handshake (DRO#version#%) and set m_dro_mode flag
- Handle CASEA chunked character-list delivery, accumulate into m_casea_buffer
  and emit a synthetic SC packet on the final empty chunk
- Trim incoming MS packets to 15 fields in DRO mode so the courtroom
  renderer doesn't receive unexpected extra fields

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: SyntaxNyah

src/aoapplication.h

@@ -84,6 +84,12 @@ class AOApplication : public QObject
   /// any.
   server::ServerData m_serverdata;
 
+  /// True when connected to a DRO (Danganronpa Online) server.
+  bool m_dro_mode = false;
+
+  /// Buffer for accumulating DRO CASEA character-list chunks before emitting SC.
+  QStringList m_casea_buffer;
+
   ///////////////loading info///////////////////
 
   // client ID. Not useful, to be removed eventually

src/packet_distribution.cpp

@@ -42,13 +42,26 @@ void AOApplication::server_packet_received(AOPacket packet)
   }
 #endif
 
-  if (header == "decryptor")
+  if (header == "DRO")
+  {
+    // DRO (Danganronpa Online) server handshake.
+    // DRO servers send "DRO#<version>#%" instead of "decryptor#NOENCRYPT#%".
+    m_dro_mode = true;
+    m_casea_buffer.clear();
+    m_serverdata.set_features(QStringList());
+    QString f_hdid = get_hdid();
+    send_server_packet(AOPacket("HI", {f_hdid}));
+    log_to_demo = false;
+  }
+  else if (header == "decryptor")
   {
     if (content.size() == 0)
     {
       return;
     }
 
+    m_dro_mode = false;
+    m_casea_buffer.clear();
     // default(legacy) values
     m_serverdata.set_features(QStringList());
 
@@ -243,6 +256,26 @@ void AOApplication::server_packet_received(AOPacket packet)
       w_courtroom->character_loading_finished();
     }
   }
+  else if (header == "CASEA")
+  {
+    // DRO servers deliver the character list in chunks via CASEA packets.
+    // Accumulate all chunks; the final chunk is signalled by an empty content list.
+    if (!is_courtroom_constructed())
+    {
+      return;
+    }
+    if (content.isEmpty())
+    {
+      // Final (empty) chunk — emit the accumulated list as a synthetic SC packet.
+      AOPacket sc_packet("SC", m_casea_buffer);
+      server_packet_received(sc_packet);
+      m_casea_buffer.clear();
+    }
+    else
+    {
+      m_casea_buffer.append(content);
+    }
+  }
   else if (header == "SM")
   {
     if (!is_courtroom_constructed() || courtroom_loaded)
@@ -391,7 +424,13 @@ void AOApplication::server_packet_received(AOPacket packet)
   {
     if (is_courtroom_constructed() && courtroom_loaded)
     {
-      w_courtroom->chatmessage_enqueue(packet.content());
+      QStringList msg_content = packet.content();
+      // DRO servers send up to 29 MS fields; AO2 courtroom only uses fields 0–14.
+      if (m_dro_mode && msg_content.size() > 15)
+      {
+        msg_content = msg_content.mid(0, 15);
+      }
+      w_courtroom->chatmessage_enqueue(msg_content);
     }
   }
   else if (header == "MC")