rebuild: split core into separate repo; move wg-go integration to internal/ctr/corebind

- go.mod: require git.zkcoi.com/zkcoi/meshray/core, replace => ../Meshray
- internal/ctr/corebind: EnhancedBind + registry + adapter (wg-go integration isolated)
- cmd/mr-wg migrated from old core/cmd/meshray-core
- core/ removed; CHANGELOG updated; fix checkdb vet warning

internal/ctr/corebind/adapter.go

@@ -0,0 +1,67 @@
+// Package corebind 的契约类型转换：在 meshray-contract 与 meshray/core 内部类型间双向转换。
+package corebind
+
+import (
+	"git.zkcoi.com/zkcoi/meshray-contract"
+	"git.zkcoi.com/zkcoi/meshray/core/connect"
+	"git.zkcoi.com/zkcoi/meshray/core/engine"
+)
+
+// 以下函数完成开源契约类型（contract 包）与 meshray/core 内部类型之间的双向转换。
+// 数值型 Layer 在 contract 与 connect 中定义一致，可直接转型。
+
+func toCoreCandidates(in []contract.Candidate) []core.Candidate {
+	out := make([]core.Candidate, 0, len(in))
+	for _, c := range in {
+		out = append(out, core.Candidate{
+			Addr:     c.Addr,
+			Type:     c.Type,
+			Priority: c.Priority,
+			Protocol: c.Protocol,
+		})
+	}
+	return out
+}
+
+func toCoreICEConfig(in contract.ICEConfig) connect.ICEConfig {
+	turn := make([]connect.TURNServerConfig, 0, len(in.TURNServers))
+	for _, s := range in.TURNServers {
+		turn = append(turn, connect.TURNServerConfig{URLs: []string{s}})
+	}
+	return connect.ICEConfig{
+		STUNServers: in.STUNServers,
+		TURNServers: turn,
+	}
+}
+
+func toCoreLayerOrder(in []contract.Layer) []connect.Layer {
+	out := make([]connect.Layer, 0, len(in))
+	for _, l := range in {
+		out = append(out, connect.Layer(l))
+	}
+	return out
+}
+
+func toContractStatus(in *core.EngineStatus) *contract.EngineStatus {
+	if in == nil {
+		return nil
+	}
+	peers := make(map[string]*contract.PeerStatus, len(in.Peers))
+	for k, v := range in.Peers {
+		peers[k] = &contract.PeerStatus{
+			PeerKey:   v.PeerKey,
+			Connected: v.Connected,
+			Layer:     v.Layer,
+		}
+	}
+	return &contract.EngineStatus{
+		PeerCount:         in.PeerCount,
+		Peers:             peers,
+		ActiveConnections: in.ActiveConnections,
+		TotalConnections:  in.TotalConnections,
+		BytesSent:         in.BytesSent,
+		BytesReceived:     in.BytesReceived,
+		StrategyFallbacks: in.StrategyFallbacks,
+		LastSwitchTime:    in.LastSwitchTime,
+	}
+}