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_parse_small_test.go

@@ -25,7 +25,6 @@ func TestParseSmallNotImplemented(t *testing.T) {
 		{"MsgMhfGetCaUniqueID", &MsgMhfGetCaUniqueID{}},
 		{"MsgMhfGetDailyMissionMaster", &MsgMhfGetDailyMissionMaster{}},
 		{"MsgMhfGetDailyMissionPersonal", &MsgMhfGetDailyMissionPersonal{}},
-		{"MsgMhfGetExtraInfo", &MsgMhfGetExtraInfo{}},
 		{"MsgMhfGetRestrictionEvent", &MsgMhfGetRestrictionEvent{}},
 		{"MsgMhfKickExportForce", &MsgMhfKickExportForce{}},
 		{"MsgMhfPaymentAchievement", &MsgMhfPaymentAchievement{}},
@@ -196,6 +195,38 @@ func TestParseSmallEnumerateHouse(t *testing.T) {
 	})
 }
 
+// TestParseSmallGetExtraInfoAndCogInfo tests that MsgMhfGetExtraInfo and
+// MsgMhfGetCogInfo correctly parse their AckHandle field.
+func TestParseSmallGetExtraInfoAndCogInfo(t *testing.T) {
+	ctx := &clientctx.ClientContext{RealClientMode: cfg.ZZ}
+
+	t.Run("GetExtraInfo", func(t *testing.T) {
+		bf := byteframe.NewByteFrame()
+		bf.WriteUint32(0xDEADBEEF)
+		_, _ = bf.Seek(0, io.SeekStart)
+		pkt := &MsgMhfGetExtraInfo{}
+		if err := pkt.Parse(bf, ctx); err != nil {
+			t.Fatalf("Parse() error = %v", err)
+		}
+		if pkt.AckHandle != 0xDEADBEEF {
+			t.Errorf("AckHandle = 0x%X, want 0xDEADBEEF", pkt.AckHandle)
+		}
+	})
+
+	t.Run("GetCogInfo", func(t *testing.T) {
+		bf := byteframe.NewByteFrame()
+		bf.WriteUint32(0xCAFEBABE)
+		_, _ = bf.Seek(0, io.SeekStart)
+		pkt := &MsgMhfGetCogInfo{}
+		if err := pkt.Parse(bf, ctx); err != nil {
+			t.Fatalf("Parse() error = %v", err)
+		}
+		if pkt.AckHandle != 0xCAFEBABE {
+			t.Errorf("AckHandle = 0x%X, want 0xCAFEBABE", pkt.AckHandle)
+		}
+	})
+}
+
 // TestParseSmallNotImplementedDoesNotPanic ensures that calling Parse on NOT IMPLEMENTED
 // packets returns an error and does not panic.
 func TestParseSmallNotImplementedDoesNotPanic(t *testing.T) {