feat(alert): 统一告警出口 TG bot + runbook [tsk_9YMHMTfWJyNB]

新增 server/internal/alert 包（15G）：
- 定义 Notifier 接口及 7 种 EventType（判封确认/补新失败/水位低/熔断/
  探针失联/心跳缺失/故障态）
- TGNotifier：Bot API 发送，Critical 事件不去重，Warning/Info 事件
  10min SETNX 去重窗口，失败重试 ≤2 次后降级至 LogNotifier
- LogNotifier：slog 结构化降级实现
- 单测：7 种事件模板 + runbook 锚点正确性；去重窗口内第二条被抑制；
  TG 5xx 重试后 fallback 且 Notify() 返回 nil；
  runbook 文件锚点与枚举一致性

接入 scheduler（替换旧的 NotifyFault 桩）：
- detect/engine.go：故障态（Rule 5）→ EventTypeFault；
  判封确认（Rule 3）→ EventTypeBlockConfirmed
- orchestrate/deps.go：Notifier 类型别名指向 alert.Notifier
- orchestrate/replacer.go：补新失败 → EventTypeReplenishFailed；
  熔断触发 → EventTypeBreakerTripped
- probe/prober_agent.go：failCount ≥3 → EventTypeProbeAgentLost
- probe/store.go：新增 CheckHeartbeats() 供 15H 检测心跳缺失>90s

新增 docs/runbook-scheduler.md：7 节各含含义/先查什么/处置/升级条件，
锚点与代码枚举对应。

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/internal/scheduler/orchestrate/replacer.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/redis/go-redis/v9"
 
+	"github.com/wangjia/pangolin/server/internal/alert"
 	"github.com/wangjia/pangolin/server/internal/scheduler/probe"
 )
 
@@ -95,7 +96,7 @@ func NewReplacer(cfg Config) *Replacer {
 		cfg.Breaker = StubBreaker{}
 	}
 	if cfg.Notifier == nil {
-		cfg.Notifier = LogNotifier{}
+		cfg.Notifier = alert.LogNotifier{}
 	}
 	if cfg.Clock == nil {
 		cfg.Clock = RealClock{}
@@ -237,11 +238,21 @@ func (r *Replacer) stepPending(ctx context.Context, uuid string, rec *ReplaceRec
 	if !r.breaker.Allow(nodeInfo.Tier, nodeInfo.Region) {
 		slog.Info("orchestrate: breaker blocked replacement",
 			"uuid", uuid, "tier", nodeInfo.Tier, "region", nodeInfo.Region)
+		// Emit 熔断触发 alert (15G exit channel).
+		ev := alert.NewEvent(alert.EventTypeBreakerTripped, rec.OldNode, map[string]string{
+			"tier":             nodeInfo.Tier,
+			"region":           nodeInfo.Region,
+			"replacement_uuid": uuid,
+		})
+		ev.Pool = nodeInfo.Tier + "/" + nodeInfo.Region
+		if notifyErr := r.notifier.Notify(ctx, ev); notifyErr != nil {
+			slog.Error("orchestrate: notify breaker tripped", "uuid", uuid, "error", notifyErr)
+		}
 		return nil // stay pending; retry next Tick
 	}
 
 	// Watermark / quota check — stub (always passes).
-	// TODO(15F): implement real capacity-quota guard here.
+	// TODO(15F): emit EventTypeWatermarkLow when real capacity guard is wired.
 
 	rec.Phase = PhaseCreating
 	rec.PhaseStartedAt = r.clock.Now()
@@ -371,9 +382,14 @@ func (r *Replacer) failProbeAttempt(ctx context.Context, uuid string, rec *Repla
 		_ = r.rdb.SRem(ctx, replaceIndexKey, uuid).Err()
 		_ = r.rdb.Expire(ctx, replaceKeyPrefix+uuid, replaceTTL).Err()
 
-		alertReason := fmt.Sprintf("probing failed after %d attempts: %s", rec.Attempts, reason)
-		if notifyErr := r.notifier.NotifyFault(ctx, rec.OldNode, alertReason); notifyErr != nil {
-			slog.Error("orchestrate: notify fault", "uuid", uuid, "error", notifyErr)
+		// Emit 补新连续失败≥3 alert (15G exit channel).
+		ev := alert.NewEvent(alert.EventTypeReplenishFailed, rec.OldNode, map[string]string{
+			"attempts":         fmt.Sprintf("%d", rec.Attempts),
+			"last_reason":      reason,
+			"replacement_uuid": uuid,
+		})
+		if notifyErr := r.notifier.Notify(ctx, ev); notifyErr != nil {
+			slog.Error("orchestrate: notify replenish failed", "uuid", uuid, "error", notifyErr)
 		}
 		slog.Error("orchestrate: replacement permanently failed — manual review required",
 			"uuid", uuid, "old_node", rec.OldNode, "attempts", rec.Attempts)