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/alert/runbook_test.go

@@ -0,0 +1,73 @@
+package alert_test
+
+import (
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/wangjia/pangolin/server/internal/alert"
+)
+
+// allEventTypes lists every EventType constant for completeness checks.
+var allEventTypes = []alert.EventType{
+	alert.EventTypeBlockConfirmed,
+	alert.EventTypeReplenishFailed,
+	alert.EventTypeWatermarkLow,
+	alert.EventTypeBreakerTripped,
+	alert.EventTypeProbeAgentLost,
+	alert.EventTypeHeartbeatMissing,
+	alert.EventTypeFault,
+}
+
+// expectedAnchors maps each EventType to the <a id="…"> expected in the runbook.
+var expectedAnchors = map[alert.EventType]string{
+	alert.EventTypeBlockConfirmed:   "block-confirmed",
+	alert.EventTypeReplenishFailed:  "replenish-failed",
+	alert.EventTypeWatermarkLow:     "watermark-low",
+	alert.EventTypeBreakerTripped:   "breaker-tripped",
+	alert.EventTypeProbeAgentLost:   "probe-agent-lost",
+	alert.EventTypeHeartbeatMissing: "heartbeat-missing",
+	alert.EventTypeFault:            "node-fault",
+}
+
+// TestRunbookAnchorsInCode verifies that every EventType produces an Event
+// whose RunbookAnchor matches the expected anchor.
+func TestRunbookAnchorsInCode(t *testing.T) {
+	for _, et := range allEventTypes {
+		e := alert.NewEvent(et, "node-x", nil)
+		wantAnchor := "#" + expectedAnchors[et]
+		if e.RunbookAnchor != wantAnchor {
+			t.Errorf("EventType %q: RunbookAnchor = %q; want %q",
+				et, e.RunbookAnchor, wantAnchor)
+		}
+	}
+}
+
+// TestRunbookFileContainsAllAnchors verifies that docs/runbook-scheduler.md
+// contains an <a id="…"> tag for every event type.
+//
+// The test is skipped when the file does not exist yet (so it never blocks CI
+// while the runbook is being drafted) and fails once the file is present but
+// an anchor is missing.
+func TestRunbookFileContainsAllAnchors(t *testing.T) {
+	// Navigate up from server/internal/alert to the repo root, then to docs/.
+	// Go test sets cwd to the package directory (server/internal/alert/),
+	// so three levels up reaches the worktree root (where docs/ lives).
+	runbookPath := "../../../docs/runbook-scheduler.md"
+
+	data, err := os.ReadFile(runbookPath)
+	if os.IsNotExist(err) {
+		t.Skip("docs/runbook-scheduler.md not found; skipping anchor check")
+	}
+	if err != nil {
+		t.Fatalf("read runbook: %v", err)
+	}
+	content := string(data)
+
+	for et, anchor := range expectedAnchors {
+		tag := `id="` + anchor + `"`
+		if !strings.Contains(content, tag) {
+			t.Errorf("runbook missing anchor for EventType %q: expected <a %s>", et, tag)
+		}
+	}
+}