fix(subagent): preserve startup cleanup failures

.agents/notes/implemented/architecture/2026-08-10-fork-children-stay-one-shot.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 .agents/notes/implemented/architecture/2026-08-10-fork-children-stay-one-shot.md
-2026-08-10-fork-children-stay-one-shot.md: f799f9f7affe7dfecbbe12d0988cf6f9b936d43e
-2026-08-10-fork-children-stay-one-shot.zh.md: 5c55e96296ed6678ac82afc0e40150d443f74c96
+2026-08-10-fork-children-stay-one-shot.md: 030bed3c1b516a54afd5f97b00000ed7ceaf64d8
+2026-08-10-fork-children-stay-one-shot.zh.md: 4b033a70c3674315c491e85be67a1d357aeac51b

.agents/notes/implemented/architecture/2026-08-10-fork-children-stay-one-shot.md

@@ -12,7 +12,7 @@ The child-scoped `report` return channel is now the largest such addition, and s
 
 ## Decision
 
-Every shipped composition binds the fork delegation tool to `backgroundMode: one-shot`: [the base bundle](../../../../packages/bundle/base/cordis.patch.yml), [the ACP example](../../../../examples/acp-agent/cordis.yml), and [the headless example](../../../../examples/headless-agent/cordis.yml). All three have access to the generic Task runtime: the base bundle leaves `run_in_background` available, while the two examples set `enableRunInBackground: false` as an explicit foreground-only composition choice.
+Every shipped composition binds the fork delegation tool to `backgroundMode: one-shot`: [the base bundle](../../../../packages/bundle/base/cordis.patch.yml), [the ACP example](../../../../examples/acp-agent/cordis.yml), and [the headless example](../../../../examples/headless-agent/cordis.yml). The base bundle leaves `run_in_background` available, because it mounts a task service; the two examples set `enableRunInBackground: false`, because they mount none and a one-shot background start would otherwise fail at call time on a missing `tasks` service.
 
 One-shot children — foreground and background alike — are created through `SubagentService.start()`, which never enters the continuable activation-setup registry, so neither `report` nor its prompt section is installed. A forked one-shot child's system prompt and tool schemas therefore equal its parent's, apart from the `persona` and `toolFilter` deltas a deployment opts into per delegation tool.
 
@@ -38,7 +38,7 @@ The reintroduction condition is recorded as a `TODO(fork-continuable-prefix-reus
 
 ## Consequences
 
-- No shipped composition creates a continuable forked child. The base bundle may return a one-shot Task id for `subagent_fork`, while the ACP and headless examples return the result to the caller's turn; `send_message` addresses only spawned children.
+- No shipped composition creates a continuable forked child; `subagent_fork` returns a result to its caller's turn, and `send_message` addresses only spawned children.
 - A forked child's request prefix stays byte-identical to its parent's unless the deployment configures `persona` or `toolFilter` on the fork delegation tool, so the token cost of seeding buys provider-side reuse again.
 - The fork provider's continuable path has no production caller and no assembled-composition coverage. It keeps its package-level tests, and the seam still accepts it, so a bundle or `--patch` overlay can reintroduce it with no code change and no warning.
 - `subagent_fork`'s model-visible schema changes: the continuable background wording is replaced by the one-shot task wording in the base bundle, and disappears entirely from the two examples. The affected keyless snapshot tool-schema sidecars are re-recorded in the same change.

.agents/notes/implemented/architecture/2026-08-10-fork-children-stay-one-shot.zh.md

@@ -12,7 +12,7 @@ fork 与 spawn 的唯一区别是 child 的 Session 会以 parent 已完成轮
 
 ## 决策
 
-所有随附组合都把 fork 委派工具绑定为 `backgroundMode: one-shot`：[base 组合包](../../../../packages/bundle/base/cordis.patch.yml)、[ACP 示例](../../../../examples/acp-agent/cordis.yml)与[headless 示例](../../../../examples/headless-agent/cordis.yml)。三者都能使用通用 Task 运行时：base 组合包保留 `run_in_background`，两个示例则把 `enableRunInBackground: false` 作为显式的仅前台组装选择。
+所有随附组合都把 fork 委派工具绑定为 `backgroundMode: one-shot`：[base 组合包](../../../../packages/bundle/base/cordis.patch.yml)、[ACP 示例](../../../../examples/acp-agent/cordis.yml)与[headless 示例](../../../../examples/headless-agent/cordis.yml)。base 组合包保留 `run_in_background`，因为它挂载了 task 服务；两个示例设置 `enableRunInBackground: false`，因为它们都不挂载 task 服务，否则一次 one-shot 后台启动会在调用时因缺少 `tasks` 服务而失败。
 
 one-shot child——前台与后台皆然——经由 `SubagentService.start()` 创建，该路径从不进入可继续的 activation setup 注册表，因此 `report` 与它的提示词 section 都不会被安装。于是一个 fork 出的 one-shot child 的系统提示词与工具 schema 与其 parent 相同，只差部署逐个委派工具主动选择的 `persona` 与 `toolFilter` 增量。
 
@@ -38,7 +38,7 @@ one-shot child——前台与后台皆然——经由 `SubagentService.start()`
 
 ## 后果
 
-- 没有任何随附组合会创建可继续的 fork child。base 组合包中的 `subagent_fork` 可以返回 one-shot Task id，而 ACP 与 headless 示例会把结果返回给调用方的轮次；`send_message` 只寻址 spawn 出的 child。
+- 没有任何随附组合会创建可继续的 fork child；`subagent_fork` 把结果返回给调用方的轮次，而 `send_message` 只寻址 spawn 出的 child。
 - 除非部署在 fork 委派工具上配置了 `persona` 或 `toolFilter`，fork child 的请求前缀与其 parent 逐字节相同，因此初始内容的 token 成本重新换来了提供方侧的复用。
 - fork 提供方的可继续路径没有生产调用方，也没有整体组装层面的覆盖。它保留自己的包内测试，seam 也仍然接受它，因此某个组合包或 `--patch` 覆盖层可以无需改动代码、也不会有任何警告地把它重新引入。
 - `subagent_fork` 面向模型的 schema 发生变化：base 组合包中可继续的后台措辞被 one-shot 的 task 措辞取代，在两个示例中则完全消失。受影响的无密钥快照工具 schema 伴随文件在同一次改动中重新记录。