refactor(subprocess): keep terminate() as the seam's only termination verb

Delete kill(signal?) from SubprocessHandle: consumers stop a process only
through terminate()'s tree-scoped SIGTERM→graceMs→SIGKILL escalation
(idempotent, also driven by the spec's abort signal, a no-op once the tree
is gone). The single-signal verb had exactly one consumer family —
lsp-local — and what it bought there was a private re-implementation of
the same escalation. The internal kill closure stays in spawn.ts as the
dispose ladder's tier primitive; terminate() now routes through it too.

lsp-local collapses onto the seam's escalation:
- LspConnection replaces its terminate()/kill() pair with one terminate()
  that delegates to handle.terminate(). Behavior change: the
  framing-failure path terminates instead of instant SIGKILL, so a
  misbehaving server now gets SIGTERM plus the killGraceMs window to
  flush before SIGKILL.
- ConnectionSpec.pipeDrainGraceMs becomes killGraceMs: one grace, the
  spawn spec's graceMs, drives both the escalation window and post-exit
  pipe draining (the provider already passed killGraceMs for it).
- LspInstance.forceTerminate() drops its hand-rolled bounded first wait
  (LSP_KILL_GRACE) and escalateProcessTree (deleted with its export and
  unit test): the seam's escalation already commits to SIGKILL after
  killGraceMs, so only the unbounded quiescence awaits stay load-bearing.

Tests: kill()-shaped spawn specs become terminate()-shaped or fold into
the terminate() suites (group-wide delivery; the settled no-op case was
already pinned by 'terminate() after the tree died'); tree-survivor
coverage is intact. A stderr-'inherit' disposition test completes the
stdout/stderr symmetry so the scoped subprocess+lsp coverage gate stands
alone instead of leaning on subagent-acp's cross-package runs.

Docs: SubprocessHandle type-equiv block, seam/impl/group READMEs, and the
consumer-migration Agent Note lose the kill(signal?) vocabulary (zh pairs
re-recorded); cordis api/services catalogs regenerated.

packages/subprocess/README.zh.md

@@ -6,7 +6,7 @@ spawn 受管子进程树的共用归属位置：完全显式的 spawn spec，其
 
 | 包（package） | ctx 键 | 角色 |
 |---|---|---|
-| [`subprocess`](subprocess/README.md)（`@deepseek-ai/dsh-subprocess`） | `ctx.subprocess` | seam 本体：抽象的 `SubprocessService.spawn(spec)`、完全显式且带按流划分 stdio 处置方式的 `SubprocessSpawnSpec`、`SubprocessHandle`（流、基于偏移量的读取器、kill/terminate/waitForExit/dispose），以及共享的凭据清除 + `DSH_*`/`CollectedOutput` 词汇 |
+| [`subprocess`](subprocess/README.md)（`@deepseek-ai/dsh-subprocess`） | `ctx.subprocess` | seam 本体：抽象的 `SubprocessService.spawn(spec)`、完全显式且带按流划分 stdio 处置方式的 `SubprocessSpawnSpec`、`SubprocessHandle`（流、基于偏移量的读取器、terminate/waitForExit/dispose），以及共享的凭据清除 + `DSH_*`/`CollectedOutput` 词汇 |
 | [`subprocess-local`](subprocess-local/README.md)（`@deepseek-ai/dsh-subprocess-local`） | 无 | 本地实现：detached 进程树、按处置方式接线的流、附带有界私有 spill 文件的尾部保留截断、`DSH_*` 合并次序、带升级的进程树信号发送、dispose 阶梯，以及先终止再等待退出的 dispose |
 
 服务拥有跨消费方重载的进程存续期；消费方拥有一个进程的含义（一条 bash 命令、未来的非 shell 运行器）以及塑造它的每一项默认值。