refactor(edge): Server 协议统一与 wsclient 收敛（Phase 3 Batch 3）

- openflare/agent/relay/flared 协议类型改为 pkg/protocol 别名，删除重复 struct
- 新增 edge/wsclient Preset 表，三组件 wsclient 改为薄包装
- 更新设计文档、计划与 changelog

pkg/protocol/server.go

@@ -1,39 +1,8 @@
 package protocol
 
-type AgentNodeSystemProfile struct {
-	Hostname         string `json:"hostname"`
-	OSName           string `json:"os_name"`
-	OSVersion        string `json:"os_version"`
-	KernelVersion    string `json:"kernel_version"`
-	Architecture     string `json:"architecture"`
-	CPUModel         string `json:"cpu_model"`
-	CPUCores         int    `json:"cpu_cores"`
-	TotalMemoryBytes int64  `json:"total_memory_bytes"`
-	TotalDiskBytes   int64  `json:"total_disk_bytes"`
-	UptimeSeconds    int64  `json:"uptime_seconds"`
-	ReportedAtUnix   int64  `json:"reported_at_unix"`
-}
-
-type AgentNodeMetricSnapshot struct {
-	CapturedAtUnix    int64   `json:"captured_at_unix"`
-	CPUUsagePercent   float64 `json:"cpu_usage_percent"`
-	MemoryUsedBytes   int64   `json:"memory_used_bytes"`
-	MemoryTotalBytes  int64   `json:"memory_total_bytes"`
-	StorageUsedBytes  int64   `json:"storage_used_bytes"`
-	StorageTotalBytes int64   `json:"storage_total_bytes"`
-	DiskReadBytes     int64   `json:"disk_read_bytes"`
-	DiskWriteBytes    int64   `json:"disk_write_bytes"`
-	NetworkRxBytes    int64   `json:"network_rx_bytes"`
-	NetworkTxBytes    int64   `json:"network_tx_bytes"`
-}
-
-type AgentNodeHealthEvent struct {
-	EventType       string            `json:"event_type"`
-	Severity        string            `json:"severity"`
-	Message         string            `json:"message"`
-	TriggeredAtUnix int64             `json:"triggered_at_unix"`
-	Metadata        map[string]string `json:"metadata"`
-}
+type AgentNodeSystemProfile = NodeSystemProfile
+type AgentNodeMetricSnapshot = NodeMetricSnapshot
+type AgentNodeHealthEvent = NodeHealthEvent
 
 type RelayProxyStat struct {
 	Name          string `json:"name"`