refactor(subprocess): rename the process seam to subprocess and address review

Review feedback (tianyicui): 'process' is a poor service name. The family is
now packages/subprocess/ — @deepseek-ai/dsh-subprocess (ctx.subprocess,
abstract SubprocessService, Subprocess* vocabulary) and
@deepseek-ai/dsh-subprocess-local (LocalSubprocessService) — renamed
throughout code, compositions, docs (en+zh, pairs re-recorded), catalogs,
and gates. 'subprocess' is the precise term for managed OS children (the
Python-stdlib sense), avoids colliding with Node's global process object,
and reads as one system beside dsh-subagent-subprocess.

ds-review-bot findings addressed:
- kill() on a settled handle is now a no-op (no signal to a possibly-reused
  pgid, no referenced grace timer delaying exit); pinned by a spy test.
- The moved DshEnvironmentKey/DshEnvironment/CollectedOutput types get
  drift-checked type-equiv blocks on the new subprocess.md page, restoring
  their manifest registration.
- subprocess.md is registered in the core.md sub-page index (en+zh).

docs/architecture.zh.md

@@ -28,7 +28,7 @@
 | `ctx.llm` | [`llm/`](../packages/llm/README.md) | 适配器注册表和模型流式调用 |
 | `ctx.tokenMeter` | [`llm/token-meter`](../packages/llm/token-meter/README.md) | 感知回放的单实例请求压力和会话表面压力 |
 | `ctx.bash` | [`bash/`](../packages/bash/README.md) | 前台和后台命令执行 |
-| `ctx.processes` | [`process/`](../packages/process/README.md) | bash 执行器之下受管理的子进程组 |
+| `ctx.subprocess` | [`process/`](../packages/subprocess/README.md) | bash 执行器之下受管理的子进程组 |
 | `ctx.pty` | [`pty/`](../packages/pty/README.md) | 按 owner 隔离的持久化终端会话 |
 | `ctx.sandbox` | [`sandbox/`](../packages/sandbox/README.md) | 同一执行环境内的进程限制（argv 包装、逐调用策略） |
 | `ctx.sandboxPolicy` | [`sandbox/`](../packages/sandbox/README.md) | 共享沙箱策略归属点 |
@@ -178,7 +178,7 @@ forever:
 |---|---|
 | 添加模型提供方 | 在 `ctx.llm` 上注册适配器 |
 | 添加面向模型的功能 | 在 `ctx.tools` 上注册；schema 进入提示词组装流程 |
-| 添加 shell 执行 | 实现并注册 `ctx.bash` 后端（本地后端通过 `ctx.processes` 生成进程） |
+| 添加 shell 执行 | 实现并注册 `ctx.bash` 后端（本地后端通过 `ctx.subprocess` 生成进程） |
 | 添加持久化终端执行 | 注册 `ctx.pty` 后端和 `dsh-tool-pty` |
 | 添加用户命令 | 在 `ctx.commands` 上注册；适配器无需模型轮次即可发现并分派该命令 |
 | 添加后台工作 | 在 `ctx.tasks` 上注册；通用 `task_*` 工具负责收集或停止 |