Support declared graceful stop and steam.update probe

- LifecycleActionTemplate 新增 gracefulStop：stop 动作可声明插件自有的优雅关闭命令、
  参数、环境、超时与 fallback；超时且 fallback=report 时任务失败，避免默认杀进程。
- 依赖探针新增 steam.update：通过 steamcmd +app_info_print 读取公开分支 buildid，
  与本地 appmanifest_<appid>.acf 比较，输出 installed/latest/update=yes|no|unknown。
- 依赖执行输入新增 ServerRoot，供探针定位插件声明的服务器安装目录。

protocol/autonomous_lifecycle.go

@@ -97,7 +97,7 @@ func ValidateRunAutonomousLifecyclePlan(plan RunAutonomousLifecyclePlan) error {
 		}
 	}
 	for _, probe := range plan.DependencyProbes {
-		if !ValidLogicalFileKey(probe.Key) || !ValidLogicalFileKey(probe.TargetKey) || !validAutonomousToken(probe.Kind, 80) || probe.MinimumVersion != "" && !validAutonomousToken(probe.MinimumVersion, 80) {
+		if !ValidLogicalFileKey(probe.Key) || !ValidLogicalFileKey(probe.TargetKey) || !validAutonomousToken(probe.Kind, 80) || probe.MinimumVersion != "" && !validAutonomousToken(probe.MinimumVersion, 80) || probe.SteamAppID != "" && !validSteamAppID(probe.SteamAppID) {
 			return ValidationError("autonomous dependency probe is invalid")
 		}
 	}
@@ -244,6 +244,18 @@ func validAutonomousTarget(osName string, arch string) bool {
 	}
 }
 
+func validSteamAppID(value string) bool {
+	if value == "" || len(value) > 10 {
+		return false
+	}
+	for _, char := range value {
+		if char < '0' || char > '9' {
+			return false
+		}
+	}
+	return true
+}
+
 func validAutonomousToken(value string, maxRunes int) bool {
 	trimmed := strings.TrimSpace(value)
 	if trimmed == "" || trimmed != value || len([]rune(value)) > maxRunes {

protocol/job.go

@@ -429,6 +429,7 @@ type DependencyProbe struct {
 	TargetKey      string   `json:"targetKey"`
 	Required       bool     `json:"required,omitempty"`
 	MinimumVersion string   `json:"minimumVersion,omitempty"`
+	SteamAppID     string   `json:"steamAppId,omitempty"`
 	Platforms      []string `json:"platforms,omitempty"`
 }
 
@@ -459,6 +460,7 @@ type DependencyExecutionInputResponse struct {
 	TargetOS         string                `json:"targetOs"`
 	TargetArch       string                `json:"targetArch"`
 	PlanDigest       string                `json:"planDigest"`
+	ServerRoot       string                `json:"serverRoot,omitempty"`
 	Probe            DependencyProbe       `json:"probe,omitempty"`
 	Plan             DependencyInstallPlan `json:"plan,omitempty"`
 	Bindings         map[string]string     `json:"bindings"`