fix(system): retired heartbeat rows no longer alarm on status page

- GET /system/health splits processes into current instances (hosts with
  a beat in the last 10 min, newest per host+kind, not stopped) and
  retiredProcesses[]; 45s stale and level only consider current ones
- heartbeat writer marks stopped_at on graceful exit (migration 0043),
  upsert clears it; pure api role now stops its writer on SIGTERM
- scheduled job system.heartbeat_cleanup (maintain, 1h) deletes rows
  without a beat for 24h and samples older than 7 days
- status page: per-role alarms ("io worker 45 秒没有心跳"), collapsible
  retired instances; glossary/runbook updated
- bump all members to 0.2.2, CHANGELOG [0.2.2]

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

docs/design/glossary.md

@@ -42,6 +42,8 @@
 | agent.propose_options | 方案;动作叫"选定",都不要叫"退回" | 选项、提案 |
 | scope.proposeFirst | 先看方案再执行 | 只要方案、只给方案、plan_only 模式 |
 | 工作流引擎的一次执行 | 运行 | run |
+| 正在写心跳的进程(process_heartbeat 当前行) | 当前实例;横幅按角色称呼:API / io worker / Agent worker / 单进程 | 活进程、在线实例 |
+| 已退出、容器已重建或被同容器新进程替换的心跳行 | 已下线实例;正常退出的标"已退出" | 历史实例、僵尸进程、死进程 |
 
 ## 文案规则