feat: configure graceful shutdown window

internal/config/config.go

@@ -19,6 +19,7 @@ type Config struct {
 	ScheduleTickInterval time.Duration // ScheduleTickInterval 计划扫描间隔，范围100ms–1m。
 	RecoveryTickInterval time.Duration // RecoveryTickInterval 执行租约恢复扫描间隔，范围100ms–1m。
 	RuntimeBatchLimit    int           // RuntimeBatchLimit 每个后台批次的候选上限，范围1–100。
+	ShutdownTimeout      time.Duration // ShutdownTimeout 优雅排空和关闭窗口，范围1s–5m。
 }
 
 func Load() (Config, error) { return FromEnv(os.Getenv) }
@@ -33,6 +34,7 @@ func FromEnv(get func(string) string) (Config, error) {
 		ScheduleTickInterval: time.Second,
 		RecoveryTickInterval: 2 * time.Second,
 		RuntimeBatchLimit:    100,
+		ShutdownTimeout:      10 * time.Second,
 	}
 	if c.HTTPAddr == "" {
 		c.HTTPAddr = "127.0.0.1:8080"
@@ -77,6 +79,13 @@ func FromEnv(get func(string) string) (Config, error) {
 		}
 		c.RuntimeBatchLimit = n
 	}
+	if raw := get("ORBIT_SHUTDOWN_TIMEOUT"); raw != "" {
+		d, err := time.ParseDuration(raw)
+		if err != nil || d < time.Second || d > 5*time.Minute {
+			return Config{}, errors.New("ORBIT_SHUTDOWN_TIMEOUT must be a duration from 1s to 5m")
+		}
+		c.ShutdownTimeout = d
+	}
 	if c.MetricsAddr != "" {
 		_, port, err := net.SplitHostPort(c.MetricsAddr)
 		n, parseErr := strconv.Atoi(port)