95cf20b00b
Implement Task 3 of MQTT orchestration: - Create MqttPacketHandlers.cs with ParseConnect(), ProcessConnect(), EnqueueConnAck(), HandleDisconnect() - Wire CONNECT and DISCONNECT dispatch in MqttParser.cs - Parse CONNECT: protocol name/level, flags, keep-alive, client ID, will, auth - Send CONNACK (4-byte fixed packet with return code) - DISCONNECT clears will message and closes connection cleanly - Auto-generate client ID for empty ID + clean session - Validate reserved bit, will flags, username/password consistency - Add Reader field to MqttHandler for per-connection parsing - 11 unit tests for CONNECT parsing and processing - 1 end-to-end integration test: TCP → CONNECT → CONNACK over the wire