refactor(edge): 抽取边缘运行时共享包并完成 Phase 3 重构

- 新增 internal/apps/edge/，三组件改为薄包装，删除 3000+ 行重复代码
- Agent 心跳周期下沉至 heartbeat/cycle.go
- 协议类型迁入 pkg/protocol/agent.go
- 补充设计文档与 changelog

internal/apps/edge/runner/wsreconnect.go

@@ -0,0 +1,64 @@
+package runner
+
+import (
+	"context"
+	"log/slog"
+	"time"
+)
+
+type WSConnection interface {
+	Close() error
+}
+
+type WSReconnectConfig struct {
+	ComponentName  string
+	ConnectBackoff time.Duration
+	ReconnectDelay time.Duration
+	OnShutdown     func()
+}
+
+func RunWSReconnectLoop(ctx context.Context, cfg WSReconnectConfig,
+	connect func(context.Context) (WSConnection, error),
+	handle func(context.Context, WSConnection),
+) error {
+	if cfg.ConnectBackoff <= 0 {
+		cfg.ConnectBackoff = 5 * time.Second
+	}
+	if cfg.ReconnectDelay <= 0 {
+		cfg.ReconnectDelay = 2 * time.Second
+	}
+	label := cfg.ComponentName
+	if label == "" {
+		label = "edge"
+	}
+
+	for {
+		select {
+		case <-ctx.Done():
+			if cfg.OnShutdown != nil {
+				cfg.OnShutdown()
+			}
+			return ctx.Err()
+		default:
+		}
+
+		conn, err := connect(ctx)
+		if err != nil {
+			slog.Error(label+" ws connect failed, will retry", "error", err)
+			SleepContext(ctx, cfg.ConnectBackoff)
+			continue
+		}
+
+		handle(ctx, conn)
+		_ = conn.Close()
+		slog.Info(label + " ws connection closed, reconnecting...")
+		SleepContext(ctx, cfg.ReconnectDelay)
+	}
+}
+
+func SleepContext(ctx context.Context, d time.Duration) {
+	select {
+	case <-ctx.Done():
+	case <-time.After(d):
+	}
+}