fix(channelserver): send ACK on empty Raviente register payload

handleMsgSysOperateRegister returned without sending an ACK when the
payload was empty, causing the client to softlock waiting for a response.
Send doAckBufSucceed with nil data on the early-return path to match
the success-path ACK type.

Also update tests to expect error returns instead of panics from
unimplemented Build/Parse stubs (matching prior panic→error refactor),
and mark resolved anti-patterns in docs.

network/binpacket/binpacket_test.go

@@ -400,16 +400,13 @@ func TestMsgBinChatAllTypes(t *testing.T) {
 	}
 }
 
-func TestMsgBinMailNotifyParsePanics(t *testing.T) {
-	defer func() {
-		if r := recover(); r == nil {
-			t.Error("Parse() should panic with 'implement me'")
-		}
-	}()
-
+func TestMsgBinMailNotifyParseReturnsError(t *testing.T) {
 	m := MsgBinMailNotify{}
 	bf := byteframe.NewByteFrame()
-	_ = m.Parse(bf)
+	err := m.Parse(bf)
+	if err == nil {
+		t.Error("Parse() should return an error (not implemented)")
+	}
 }
 
 func TestMsgBinMailNotifyBuildLongName(t *testing.T) {

network/binpacket/msg_bin_mail_notify_test.go

@@ -102,19 +102,15 @@ func TestMsgBinMailNotify_Build(t *testing.T) {
 	}
 }
 
-func TestMsgBinMailNotify_Parse_Panics(t *testing.T) {
-	// Document that Parse() is not implemented and panics
+func TestMsgBinMailNotify_Parse_ReturnsError(t *testing.T) {
+	// Document that Parse() is not implemented and returns an error
 	msg := MsgBinMailNotify{}
 	bf := byteframe.NewByteFrame()
 
-	defer func() {
-		if r := recover(); r == nil {
-			t.Error("Parse() did not panic, but should panic with 'implement me'")
-		}
-	}()
-
-	// This should panic
-	_ = msg.Parse(bf)
+	err := msg.Parse(bf)
+	if err == nil {
+		t.Error("Parse() should return an error (not implemented)")
+	}
 }
 
 func TestMsgBinMailNotify_BuildMultiple(t *testing.T) {

network/mhfpacket/msg_opcode_coverage_test.go

@@ -1,6 +1,7 @@
 package mhfpacket
 
 import (
+	"strings"
 	"testing"
 
 	"erupe-ce/common/byteframe"
@@ -261,7 +262,8 @@ func TestBuildCoverage_NotImplemented(t *testing.T) {
 				return
 			}
 			// Build returned an error, which is expected for NOT IMPLEMENTED stubs
-			if err.Error() != "NOT IMPLEMENTED" {
+			errMsg := err.Error()
+			if errMsg != "NOT IMPLEMENTED" && !strings.Contains(errMsg, "not implemented") {
 				t.Errorf("Build() returned unexpected error: %v", err)
 			}
 		})