feat(system): process heartbeat + /system/health, engine runs business fields (W9-I)

- process_heartbeat / process_heartbeat_sample (0034): api / worker / worker:agent / all
  upsert every 15s (event loop lag last/max, concurrency, running runs, SSE connections, memory)
- GET /system/health (admin): processes with 45s stale flag, SSE, DB latency/size/connections,
  disks (DATA_DIR / library roots / download dirs, cache thresholds), mount sentinel checks
  with IO timeout, engine pending/oldest/24h failure rate, schedules
- GET /system/health/history?hours=: bucketed lag / running / SSE series
- /engine/runs and /engine/runs/{id}: business {kind, refId, title, triggeredBy} joined from
  run input / task / agent_run / tasks_run_meta / outbox; businessKind / businessRefId filters
- docs/runbook/ops.md: field meanings and alert thresholds

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/contracts/test/db-sync.test.ts

@@ -127,6 +127,9 @@ const INTERNAL_TABLES = [
   "AdminSession",
   "LoginAttempt",
   "SseEvent",
+  // W9-I 进程心跳(0034):服务端内部,经 /system/health 的专用 DTO 暴露
+  "ProcessHeartbeat",
+  "ProcessHeartbeatSample",
 ];
 const INTERNAL_ENUMS = ["TasksOpLedgerStatus"];
 
@@ -209,6 +212,7 @@ const ENUMS: Record<string, z.ZodEnum> = {
   ReconcileRunMode: C.ReconcileMode,
   ReconcileRunStatus: C.ReconcileStatus,
   SecretPurpose: C.SecretPurpose,
+  ProcessHeartbeatProcessKind: C.ProcessKind,
   ScheduledJobBoardGroup: C.ScheduleGroup,
   ScheduledJobKind: C.ScheduleKind,
   ScheduledJobLastStatus: C.ScheduleRunStatus,