fix(items): stop G-rank Workshop/Cog softlock on missing ACK

MSG_MHF_GET_EXTRA_INFO (0xA6) and MSG_MHF_GET_COG_INFO (0xC3) had
Parse() returning NOT IMPLEMENTED. The dispatch loop treats any Parse
error as a hard drop — no ACK is ever sent, so the client waits
indefinitely and effectively soft-locks when entering the G-rank
Workshop or Master Felyne (Cog) screens.

Fix: parse AckHandle (the only field we can confirm from the protocol)
and respond with doAckBufFail so the client receives a well-formed
buf-type ACK with error code 1. The client's fail branch for these
requests exits cleanly without reading response fields, avoiding the
read-past-EOF crash that an empty success ACK would cause.

The full response format for both packets is still unknown; a complete
implementation requires further RE. The TODO comments mark the gap.

Fixes #180.

network/mhfpacket/msg_comprehensive_test.go

@@ -495,6 +495,8 @@ func TestAckHandlePacketsParse(t *testing.T) {
 		{"MsgMhfGetUdSchedule", network.MSG_MHF_GET_UD_SCHEDULE},
 		{"MsgMhfGetUdInfo", network.MSG_MHF_GET_UD_INFO},
 		{"MsgMhfGetKijuInfo", network.MSG_MHF_GET_KIJU_INFO},
+		{"MsgMhfGetExtraInfo", network.MSG_MHF_GET_EXTRA_INFO},
+		{"MsgMhfGetCogInfo", network.MSG_MHF_GET_COG_INFO},
 	}
 
 	ctx := &clientctx.ClientContext{RealClientMode: cfg.ZZ}