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_test.go

@@ -11,6 +11,7 @@ import (
 	"github.com/alicebob/miniredis/v2"
 	"github.com/redis/go-redis/v9"
 
+	"github.com/wangjia/pangolin/server/internal/alert"
 	"github.com/wangjia/pangolin/server/internal/scheduler/orchestrate"
 	"github.com/wangjia/pangolin/server/internal/scheduler/probe"
 )
@@ -267,21 +268,35 @@ func passingSnapshots() map[string]probe.ProbeSnapshot {
 // ─────────────────────────────────────────────────────────────────────────────
 
 type mockNotifier struct {
-	mu    sync.Mutex
-	calls []string
+	mu     sync.Mutex
+	events []alert.Event
 }
 
-func (n *mockNotifier) NotifyFault(_ context.Context, nodeID, _ string) error {
+func (n *mockNotifier) Notify(_ context.Context, e alert.Event) error {
 	n.mu.Lock()
 	defer n.mu.Unlock()
-	n.calls = append(n.calls, nodeID)
+	n.events = append(n.events, e)
 	return nil
 }
 
+// count returns the number of Notify calls received.
 func (n *mockNotifier) count() int {
 	n.mu.Lock()
 	defer n.mu.Unlock()
-	return len(n.calls)
+	return len(n.events)
+}
+
+// countByType returns the number of Notify calls with the given EventType.
+func (n *mockNotifier) countByType(t alert.EventType) int {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	c := 0
+	for _, e := range n.events {
+		if e.Type == t {
+			c++
+		}
+	}
+	return c
 }
 
 // ─────────────────────────────────────────────────────────────────────────────
@@ -557,9 +572,9 @@ func TestProbeFailMaxAttempts(t *testing.T) {
 		}
 	}
 
-	// NotifyFault must be called exactly once.
-	if n := h.notifier.count(); n != 1 {
-		t.Errorf("NotifyFault calls = %d; want 1", n)
+	// Notify(EventTypeReplenishFailed) must be called exactly once.
+	if n := h.notifier.countByType(alert.EventTypeReplenishFailed); n != 1 {
+		t.Errorf("Notify(ReplenishFailed) calls = %d; want 1", n)
 	}
 
 	// Record must be in failed phase.