test: import 38 channelserver test files from v9.2.x-stable

Port test files from v9.2.x-stable branch to increase channelserver
coverage from 13.8% to 25.6% (556 tests passing).

Adapted all files to main's struct definitions: config import alias,
Airou/CatDefinition rename, packet field mismatches, Raviente struct
differences, and maxPlayers defaults. Removed tests referencing
production code not yet on main (Player, FestivalColour, etc.).
Excluded handlers_register_test.go (Raviente completely redesigned).

server/channelserver/test_helpers_test.go

@@ -0,0 +1,68 @@
+package channelserver
+
+import (
+	"net"
+
+	"erupe-ce/common/byteframe"
+	_config "erupe-ce/config"
+	"erupe-ce/network"
+	"erupe-ce/network/clientctx"
+
+	"go.uber.org/zap"
+)
+
+// mockPacket implements mhfpacket.MHFPacket for testing.
+// Imported from v9.2.x-stable.
+type mockPacket struct {
+	opcode uint16
+}
+
+func (m *mockPacket) Opcode() network.PacketID {
+	return network.PacketID(m.opcode)
+}
+
+func (m *mockPacket) Build(bf *byteframe.ByteFrame, ctx *clientctx.ClientContext) error {
+	if ctx == nil {
+		panic("clientContext is nil")
+	}
+	bf.WriteUint32(0x12345678)
+	return nil
+}
+
+func (m *mockPacket) Parse(bf *byteframe.ByteFrame, ctx *clientctx.ClientContext) error {
+	return nil
+}
+
+// createMockServer creates a minimal Server for testing.
+// Imported from v9.2.x-stable and adapted for main.
+func createMockServer() *Server {
+	logger, _ := zap.NewDevelopment()
+	s := &Server{
+		logger:      logger,
+		erupeConfig: &_config.Config{},
+		stages:      make(map[string]*Stage),
+		sessions:    make(map[net.Conn]*Session),
+		raviente: &Raviente{
+			register: make([]uint32, 30),
+			state:    make([]uint32, 30),
+			support:  make([]uint32, 30),
+		},
+	}
+	s.i18n = getLangStrings(s)
+	return s
+}
+
+// createMockSession creates a minimal Session for testing.
+// Imported from v9.2.x-stable and adapted for main.
+func createMockSession(charID uint32, server *Server) *Session {
+	logger, _ := zap.NewDevelopment()
+	return &Session{
+		charID:        charID,
+		clientContext: &clientctx.ClientContext{},
+		sendPackets:   make(chan packet, 20),
+		Name:          "TestPlayer",
+		server:        server,
+		logger:        logger,
+		semaphoreID:   make([]uint16, 2),
+	}
+}