refactor: remove per-followup result attribution

packages/subagent/subagent-inprocess/README.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/subagent/subagent-inprocess/README.md
-README.md: 980bc18de088c41dfe2f57a5ff0882a60892fc9f
-README.zh.md: 1ceb628371c3ae9cee6d8afa6bc1d95ba4cda8ae
+README.md: 67f0cf5dd1ecb18542af56953a0eaa40988aca0d
+README.zh.md: 58998ce06cd724d6a1f96f08ba31c5da30007b1b

packages/subagent/subagent-inprocess/README.md

@@ -14,10 +14,12 @@ The driver follows this sequence:
 2. Call `parent.ctx.agents.create` directly, passing the required request signal into the factory's creation transaction.
 3. During that transaction's unpublished setup window, install the requested persona, tool restriction, and structured-output runtime.
 4. Publish the child, retain the returned `AgentHandle`, and drive one task with `child.followup(prompt)` followed by `child.whenIdle()`.
-5. Read the child's own last assistant message and latest message-triggered turn reason, excluding any fork seed and later between-turn records.
+5. Read the child's own last assistant message and final durable turn reason from the complete owned child run, excluding any fork seed.
 
 The child gets the parent's working-directory/session lineage and inherits the parent provider, model, and output-token cap unless `request.agentOptions` overrides them. It gets a fresh flat registration scope: parent ownership does not import parent tool restrictions or establish an authority subset.
 
+This result boundary is valid because the provider owns an isolated child lifecycle from publication through quiescence. Steering submitted during that lifecycle belongs to the child run; the provider does not pretend the initial follow-up alone owns its output.
+
 When the optional sandbox-policy or approval service is composed, the driver snapshots the parent's explicit session override before child creation and appends a source-tagged event during unpublished setup, after any fork history and before session publication. It never copies deployment defaults or one-shot grants; later child switches still win. See the [policy-inheritance decision](../../../.agents/notes/implemented/feature/2026-07-25-subagent-policy-inheritance.md).
 
 ## Cancellation and ownership

packages/subagent/subagent-inprocess/README.zh.md

@@ -14,10 +14,12 @@
 2. 直接调用 `parent.ctx.agents.create`，把必需的请求信号传入工厂的创建事务。
 3. 在该事务未发布的设置窗口中，安装请求的 persona、工具限制和结构化输出运行时。
 4. 发布子 agent，保留返回的 `AgentHandle`，并通过先调用 `child.followup(prompt)`、再调用 `child.whenIdle()` 来驱动一项任务。
-5. 读取子 agent 自身最后一条 assistant 消息，以及由消息触发的最新轮次原因；排除任何 fork 初始内容和后续轮次间记录。
+5. 从完整的自有子运行中读取子 agent 自身最后一条 assistant 消息和最终持久轮次原因，并排除任何 fork 初始内容。
 
 子 agent 会获得父 agent 的工作目录／会话谱系；除非 `request.agentOptions` 覆盖，否则还会继承父 agent 的提供方、模型和输出 token 上限。它获得全新的扁平注册作用域：父级所有权不会导入父 agent 的工具限制，也不会建立权限子集。
 
+该结果边界成立，是因为提供方拥有从发布到完全停稳的隔离子 agent 生命周期。在该生命周期内提交的 steering（中途引导）属于子运行；提供方不会声称输出只归初始 follow-up 所有。
+
 当组合中挂载了可选的沙箱策略或审批服务时，驱动器会在创建子 agent 前对父级的显式会话覆盖项获取快照，并在未发布的设置阶段追加一条带来源标记的事件，使其位于所有 fork 历史之后、会话发布之前。它绝不复制部署默认值或一次性授权；子 agent 后续的切换仍然优先。参见[策略继承决策](../../../.agents/notes/implemented/feature/2026-07-25-subagent-policy-inheritance.md)。
 
 ## 取消与所有权