[manager] add safe asynchronous CopyGA

docs/README.md

@@ -7,6 +7,7 @@
 - [ReportEvent / GetHostCacheState 小 block 性能记录](design/report_event_performance.md) - local/Redis 指标解释、锁与可见性语义、有界并发、容量基准及后续优化边界
 - [高可用与选主机制](design/ha_leader_elector.md) - HA 架构、LeaderElector 状态机、CoordinationBackend、Leader 发现
 - [CacheReclaimer 异步删除与过度逐出优化](design/cache_reclaimer_async_delete.md) - 异步删除生命周期、in-flight credit、反压与无进展退避
+- [KVCM × PACE CopyGA 异步化设计](design/async_copyga.md) - 复用 PACE 现有异步接口的 KVCM 端到端异步方案、持久 guard fencing、drain-safe 回收、quarantine 容量门控与恢复
 - [后台扫描 GC](design/cache_garbage_collector.md) - 基于 authoritative cursor 的后台全量巡检；V1 清理长期 orphan WRITING 和普通 SERVING storage-missing，并提供无副作用读取、精确值条件 CAS 与 HA 生命周期
 
 ### 开发文档

docs/api/admin_service.md

@@ -337,6 +337,49 @@ curl -g -vvv -X POST http://localhost:6492/api/removeCache \
 }'
 ```
 
+## List Async Copy Quarantine
+
+Lists asynchronous Copy operations whose remote drain cannot yet be proven. An empty
+`instance_group_name` lists every group. This API is read-only; timeout or record age does not make a target safe to
+reuse.
+
+```bash
+curl -g -vvv -X POST http://localhost:6492/api/listAsyncCopyQuarantine \
+  -H "Content-Type: application/json" \
+  -H "Accept: application/json" \
+  -d '{
+    "trace_id": "list_async_copy_quarantine_01",
+    "instance_group_name": "test_group"
+}'
+```
+
+Each returned record identifies the exact operation, source and target locations, backend task IDs, guarded bytes,
+guard timestamps and the last error.
+
+## Break-glass Release Async Copy
+
+This is a privileged recovery API for an `UNKNOWN` asynchronous Copy guard. Use it only after an independent external
+fencing procedure proves that the old remote operation can never resume writing its target. Operator confirmation or
+elapsed time alone is not sufficient evidence. The request is rejected unless all evidence fields are non-empty and
+`external_fencing_confirmed` is `true`.
+
+```bash
+curl -g -vvv -X POST http://localhost:6492/api/breakGlassReleaseAsyncCopy \
+  -H "Content-Type: application/json" \
+  -H "Accept: application/json" \
+  -d '{
+    "trace_id": "break_glass_async_copy_01",
+    "operation_id": "operation-id-from-list-api",
+    "operator_name": "operator-name",
+    "external_fencing_evidence": "change-ticket-or-fencing-record",
+    "external_fencing_confirmed": true
+}'
+```
+
+The Manager performs an exact compare-and-set on operation ID and guard state, writes an audit log, and only then
+releases the quarantined target. See [KVCM × PACE CopyGA asynchronous design](../design/async_copyga.md) for the guard,
+recovery and rollback contract.
+
 ## Register Instance
 ```bash
 curl -g -vvv -X POST http://localhost:6492/api/registerInstance \