docs(subagent): distinguish execution results from cleanup failure signals

The subsystem result paragraph still said that a parent log records the
final cleanup-failure status and that the result had already been returned.
The manager instead captures the execution result, performs cleanup, sends
that preserved result in the parent notice, and then resolves the public
result. Cleanup failure separately rejects dispose and marks the live
subagent/end event as error.

Correct the bilingual paragraph to name those actual recipients and timing.
Do not imply that the successful execution notice becomes a failed notice,
or change the runtime's independent execution/cleanup outcomes.

Validation: the updated bilingual pair passes. The statement is checked
against finishDisposal/notifySettlement and the existing cleanup-failure
regressions; final documentation gates run before publication.

docs/subsystems/subagent.i18n.yaml

@@ -18,8 +18,8 @@
   en: 30c3607a969696ce
   zh: e6359cdf22b1e235
 /subagents/results-and-backend-handles:
-  en: efa1c1940344d365
-  zh: f6f06792ef2699c0
+  en: 69ea5bed7d9fb64a
+  zh: b187a822b813e80a
 /subagents/the-provider-contract-subagentprovider:
   en: 226ba8094a8cf96c
   zh: 719678662905d1eb

docs/subsystems/subagent.md

@@ -226,7 +226,7 @@ type SubagentInterruptAuthority =
 
 ## Results and backend handles
 
-SubagentResult is available to program consumers. The activation registry retains the external backend handle until disposal completes. A cleanup failure does not overwrite an already returned result; the parent log retains that output and records the final failure status. Backend-owned diagnostics must satisfy the safe-detail requirements below.
+SubagentResult is available to program consumers. The activation registry retains the external backend handle until disposal completes. A cleanup failure does not replace a captured execution result: the activation result and parent notice retain it, while dispose rejects and the live subagent/end event reports error. Backend-owned diagnostics must satisfy the safe-detail requirements below.
 
 ```ts type-equiv
 /**

docs/subsystems/subagent.zh.md

@@ -226,7 +226,7 @@ type SubagentInterruptAuthority =
 
 ## 结果与后端句柄
 
-SubagentResult 供程序消费方读取。activation 注册表保留外部后端句柄，直到释放完成。清理失败不会覆盖已经返回的结果；父日志保留该输出并记录最终失败状态。后端提供的诊断必须满足下述安全信息要求。
+SubagentResult 供程序消费方读取。activation 注册表保留外部后端句柄，直到释放完成。清理失败不会覆盖已捕获的执行结果：activation 结果与父级通知保留该结果，dispose 拒绝，而在线 subagent/end 事件报告 error。后端提供的诊断必须满足下述安全信息要求。
 
 ```ts type-equiv
 /**